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Question 1Differentiation
What is the derivative of sin x with respect to x?
- −sin x
- sec^2 x
- −cos x
- cos x Correct answer.
Explanation
The standard derivative formula for the sine function is d/dx(sin x) = cos x. This is a fundamental result in differentiation of trigonometric functions.
Question 2Differentiation
If y = e^(3x), what is dy/dx?
- e^(3x)/3
- e^(3x)
- 3e^(3x) Correct answer.
- 3x e^(3x)
Explanation
For y = e^(kx), the derivative is k e^(kx). Here k = 3, so dy/dx = 3e^(3x).
Question 3Differentiation
What is the derivative of ln x for x > 0?
- 1/x Correct answer.
- ln x
- 1/ln x
- x
Explanation
The natural logarithm function has derivative d/dx(ln x) = 1/x for x > 0. This follows from the inverse relationship between ln x and e^x.
Question 4Differentiation
If f(x) = 5x^2 − 3x + 7, what is f'(x)?
- 10x^2 − 3
- 10x − 3 Correct answer.
- 5x − 3
- 10x + 7
Explanation
Differentiate term by term: d/dx(5x^2) = 10x, d/dx(−3x) = −3, and d/dx(7) = 0. Hence f'(x) = 10x − 3.
Question 5Differentiation
The derivative of a constant function f(x) = c is:
- c
- 0 Correct answer.
- 1
- undefined
Explanation
A constant function has the same value for all x, so its graph is a horizontal line with slope zero. Therefore its derivative is 0 everywhere.
Question 6Differentiation
If y = x^2 + 3x, what is the value of dy/dx at x = 1?
- 2
- 4
- 3
- 5 Correct answer.
Explanation
Differentiating gives dy/dx = 2x + 3. Substituting x = 1 yields 2(1) + 3 = 5.
Question 7Differentiation
What is the derivative of cos x with respect to x?
- sin x
- −cos x
- −sin x Correct answer.
- tan x
Explanation
The standard derivative formula is d/dx(cos x) = −sin x. The negative sign is essential and distinguishes it from the derivative of sin x.
Question 8Differentiation
If y = (2x + 1)^5, what is dy/dx?
- (2x + 1)^4
- 10(2x + 1)^4 Correct answer.
- 2(2x + 1)^4
- 5(2x + 1)^4
Explanation
Apply the chain rule: differentiate the outer power to get 5(2x + 1)^4, then multiply by the derivative of the inner function 2x + 1, which is 2. This gives 10(2x + 1)^4.
Question 9Differentiation
If y = sin(3x), what is dy/dx?
- cos(3x)
- 3 sin(3x)
- 3 cos(3x) Correct answer.
- −3 cos(3x)
Explanation
By the chain rule, d/dx[sin(u)] = cos(u) · du/dx. With u = 3x, du/dx = 3, so dy/dx = 3 cos(3x).
Question 10Differentiation
If y = x^2 e^x, what is dy/dx?
- e^x(x^2 + 2x) Correct answer.
- x^2 e^x
- e^x(x^2 − 2x)
- 2x e^x
Explanation
Use the product rule: (uv)' = u'v + uv'. Here u = x^2, v = e^x, so u' = 2x and v' = e^x. Thus dy/dx = 2x e^x + x^2 e^x = e^x(x^2 + 2x).
Question 11Differentiation
If y = (x^2 + 1)/(x − 1), what is dy/dx?
- (2x)/(x − 1)^2
- (x^2 − 2x − 1)/(x − 1)^2 Correct answer.
- (x^2 + 2x + 1)/(x − 1)^2
- (2x)/(1)
Explanation
By the quotient rule, dy/dx = [(2x)(x − 1) − (x^2 + 1)(1)]/(x − 1)^2. Expanding the numerator gives 2x^2 − 2x − x^2 − 1 = x^2 − 2x − 1, so dy/dx = (x^2 − 2x − 1)/(x − 1)^2.
Question 12Differentiation
If x^2 + y^2 = 25, what is dy/dx?
- x/y
- −y/x
- 2x + 2y
- −x/y Correct answer.
Explanation
Differentiate both sides implicitly with respect to x: 2x + 2y(dy/dx) = 0. Solving for dy/dx gives dy/dx = −x/y.
Question 13Differentiation
If y = log_10 x, what is dy/dx?
- 1/x
- 1/(x ln 10) Correct answer.
- ln 10 / x
- 10/x
Explanation
The derivative of log_a x is 1/(x ln a). For a = 10, this gives dy/dx = 1/(x ln 10).
Question 14Differentiation
If y = tan x, what is dy/dx?
- cot x
- −csc^2 x
- sec x tan x
- sec^2 x Correct answer.
Explanation
The standard derivative formula for tan x is sec^2 x. This can be derived by writing tan x = sin x / cos x and applying the quotient rule.
Question 15Differentiation
If y = e^(sin x), what is dy/dx?
- e^(cos x)
- e^(sin x) cos x Correct answer.
- e^(sin x) sin x
- cos x
Explanation
By the chain rule, d/dx[e^(u)] = e^(u) · du/dx. With u = sin x, du/dx = cos x, so dy/dx = e^(sin x) cos x.
Question 16Differentiation
If y = x ln x, what is dy/dx?
- 1/x
- 1 + x
- ln x + 1 Correct answer.
- ln x
Explanation
Use the product rule with u = x and v = ln x: u' = 1, v' = 1/x. Then dy/dx = 1·ln x + x·(1/x) = ln x + 1.
Question 17Differentiation
If y = sin^2 x, what is dy/dx?
- sin 2x Correct answer.
- 2 cos x
- cos^2 x
- 2 sin x
Explanation
Using the chain rule with u = sin x, dy/dx = 2 sin x · cos x. By the double-angle identity, this equals sin 2x.
Question 18Differentiation
If y = (x + 1)/(x − 1), what is dy/dx at x = 2?
- 2
- −2 Correct answer.
- −1
- 1
Explanation
By the quotient rule, dy/dx = [(1)(x − 1) − (x + 1)(1)]/(x − 1)^2 = −2/(x − 1)^2. At x = 2 this equals −2/1 = −2.
Question 19Differentiation
If y = sqrt(x^2 + 1), what is dy/dx?
- 1/(2√(x^2 + 1))
- x√(x^2 + 1)
- 2x/√(x^2 + 1)
- x/√(x^2 + 1) Correct answer.
Explanation
Write y = (x^2 + 1)^(1/2). The chain rule gives dy/dx = (1/2)(x^2 + 1)^(−1/2) · 2x = x/√(x^2 + 1).
Question 20Differentiation
If y = x^x for x > 0, what is dy/dx?
- x^x
- x^x (1 + ln x) Correct answer.
- x·x^(x−1)
- x^x ln x
Explanation
Take ln y = x ln x and differentiate implicitly: (1/y)(dy/dx) = ln x + 1. Hence dy/dx = y(1 + ln x) = x^x(1 + ln x).
Question 21Differentiation
For the curve y = x^3 − 3x, at which values of x is the tangent horizontal?
- x = ±1 Correct answer.
- x = 0 only
- x = 3 only
- x = ±√3
Explanation
A horizontal tangent occurs where dy/dx = 0. Here dy/dx = 3x^2 − 3 = 3(x^2 − 1), which is zero at x = ±1.
Question 22Differentiation
If y = sin^(−1) x for −1 < x < 1, what is dy/dx?
- 1/√(1 − x^2) Correct answer.
- −1/√(1 − x^2)
- √(1 − x^2)
- 1/(1 + x^2)
Explanation
The derivative of the inverse sine function is 1/√(1 − x^2) for −1 < x < 1. This follows from differentiating x = sin y implicitly.
Question 23Differentiation
If x = a(θ − sin θ) and y = a(1 − cos θ), what is dy/dx?
- cot(θ/2) Correct answer.
- tan(θ/2)
- sin θ
- 1 − cos θ
Explanation
Parametric differentiation gives dy/dx = (dy/dθ)/(dx/dθ) = [a sin θ]/[a(1 − cos θ)] = sin θ/(1 − cos θ). Using half-angle identities this simplifies to cot(θ/2).
Question 24Differentiation
If y = e^(2x) sin 3x, what is dy/dx?
- e^(2x)(2 sin 3x + 3 cos 3x) Correct answer.
- e^(2x)(2 sin 3x − 3 cos 3x)
- 2e^(2x) sin 3x
- 3e^(2x) cos 3x
Explanation
Apply the product rule: (uv)' = u'v + uv' with u = e^(2x) and v = sin 3x. Then u' = 2e^(2x) and v' = 3 cos 3x, so dy/dx = e^(2x)(2 sin 3x + 3 cos 3x).
Question 25Differentiation
If y = a^x, where a > 0 and a ≠ 1, what is dy/dx?
- a^x
- x a^(x−1)
- a^x ln a Correct answer.
- a^x / ln a
Explanation
For an exponential function with constant base a, the derivative is the function itself multiplied by the natural logarithm of the base. This follows from writing a^x = e^(x ln a) and applying the chain rule. The power rule applies only when the exponent is a constant, not a variable.
Question 26Differentiation
If y = cot x, what is dy/dx?
- −cosec x cot x
- cosec^2 x
- sec^2 x
- −cosec^2 x Correct answer.
Explanation
The derivative of cot x is −cosec^2 x, which can be obtained by writing cot x = cos x / sin x and applying the quotient rule. The negative sign is essential because cot x is decreasing on each interval where it is defined.
Question 27Differentiation
If y = log(sin x) for sin x > 0, what is dy/dx?
- cosec x
- cot x Correct answer.
- tan x
- sec x
Explanation
Using the chain rule, differentiate the outer logarithm to get 1/sin x, then multiply by the derivative of sin x, which is cos x. This gives cos x / sin x = cot x. The condition sin x > 0 ensures the logarithm is defined.
Question 28Differentiation
If x = a(cos θ + θ sin θ) and y = a(sin θ − θ cos θ), where a is a positive constant, what is dy/dx?
- cot θ
- tan θ Correct answer.
- sec θ
- θ tan θ
Explanation
Differentiate parametrically: dx/dθ = a(−sin θ + sin θ + θ cos θ) = aθ cos θ, and dy/dθ = a(cos θ − cos θ + θ sin θ) = aθ sin θ. Dividing gives dy/dx = (aθ sin θ)/(aθ cos θ) = tan θ, for θ ≠ 0 and cos θ ≠ 0.
Question 29Applications of Derivatives
Find the slope of the tangent to the curve y = x³ − 3x at the point where x = 2.
- 12
- 3
- 6
- 9 Correct answer.
Explanation
The slope of the tangent is the value of dy/dx at the given point. Here dy/dx = 3x² − 3, so at x = 2 the slope equals 3(4) − 3 = 9.
Question 30Applications of Derivatives
A function f is defined on an interval containing c. Which condition guarantees that f has a local maximum at c?
- f′(c) = 0 and f″(c) > 0
- f′(c) < 0 and f″(c) < 0
- f′(c) > 0 and f″(c) = 0
- f′(c) = 0 and f″(c) < 0 Correct answer.
Explanation
The second derivative test states that if f′(c) = 0 and f″(c) < 0, the curve is concave downward at c, so f has a local maximum there. A stationary point with negative concavity is a peak, not a trough.
Question 31Applications of Derivatives
The radius r of a circle increases at the constant rate of 2 cm/s. At what rate is the area increasing when r = 5 cm?
- 20π cm²/s Correct answer.
- 25π cm²/s
- 10π cm²/s
- 4π cm²/s
Explanation
The area is A = πr², so dA/dt = 2πr · dr/dt by the chain rule. Substituting r = 5 and dr/dt = 2 gives dA/dt = 2π(5)(2) = 20π cm²/s.
Question 32Applications of Derivatives
For the function f(x) = x² − 4x + 7, at which value of x does f have a stationary point?
- x = −2
- x = 7
- x = 4
- x = 2 Correct answer.
Explanation
Stationary points satisfy f′(x) = 0. Here f′(x) = 2x − 4, which vanishes at x = 2. At that point f has a local minimum.
Question 33Applications of Derivatives
The derivative of a differentiable function is positive on (a, b). What can be concluded about f on that interval?
- f is strictly decreasing on (a, b)
- f has a local maximum at every point of (a, b)
- f is constant on (a, b)
- f is strictly increasing on (a, b) Correct answer.
Explanation
A positive derivative on an interval means the function rises as x increases, so f is strictly increasing there. This is the first derivative test for monotonicity.
Question 34Applications of Derivatives
Evaluate the limit lim(x→0) (sin 3x)/x.
- 1
- 0
- 1/3
- 3 Correct answer.
Explanation
Using the standard limit lim(t→0)(sin t)/t = 1, write (sin 3x)/x = 3 · (sin 3x)/(3x). As x→0 the fraction tends to 1, so the limit is 3.
Question 35Applications of Derivatives
A particle moves along a line with position s(t) = t³ − 6t² + 9t. At which time is its acceleration zero?
- t = 2 Correct answer.
- t = 3
- t = 1
- t = 0
Explanation
Velocity is s′(t) = 3t² − 12t + 9 and acceleration is s″(t) = 6t − 12. Setting 6t − 12 = 0 gives t = 2.
Question 36Applications of Derivatives
Which of the following is an indeterminate form to which l'Hôpital's rule may be applied directly?
- 0 · 5
- 2/3
- 0/0 Correct answer.
- 1/0
Explanation
L'Hôpital's rule applies to the indeterminate forms 0/0 and ∞/∞. A form such as 1/0 is not indeterminate but tends to infinity in magnitude.
Question 37Applications of Derivatives
Find the equation of the tangent to the curve y = x² + 2x at the point (1, 3).
- y = 2x + 1
- y = 3x
- y = 4x − 1 Correct answer.
- y = 4x + 1
Explanation
Here dy/dx = 2x + 2, so the slope at x = 1 is 4. Using point-slope form with (1, 3): y − 3 = 4(x − 1), which simplifies to y = 4x − 1.
Question 38Applications of Derivatives
The function f(x) = x³ − 3x² + 4 is examined for concavity. On which interval is the curve concave upward?
- (−∞, ∞)
- (1, ∞) Correct answer.
- (−∞, 1)
- (0, 2)
Explanation
Compute f′(x) = 3x² − 6x and f″(x) = 6x − 6. The curve is concave upward where f″(x) > 0, that is 6x − 6 > 0, giving x > 1.
Question 39Applications of Derivatives
A ladder 13 m long rests against a vertical wall. Its foot slides away from the wall at 2 m/s. How fast is the top sliding down when the foot is 5 m from the wall?
- 12/5 m/s
- 5/6 m/s Correct answer.
- 2 m/s
- 6/5 m/s
Explanation
With x the foot distance and y the height, x² + y² = 169. Differentiating gives 2x dx/dt + 2y dy/dt = 0, so dy/dt = −(x/y)(dx/dt). When x = 5, y = 12, giving dy/dt = −(5/12)(2) = −5/6, so the top descends at 5/6 m/s.
Question 40Applications of Derivatives
Evaluate lim(x→0) (e^x − 1 − x)/x².
- 1/2 Correct answer.
- 0
- 1
- 2
Explanation
The form is 0/0, so apply l'Hôpital's rule twice. First derivative ratio: (e^x − 1)/(2x), still 0/0; second: e^x/2, which tends to 1/2 as x→0.
Question 41Applications of Derivatives
The function f(x) = 2x³ − 9x² + 12x has critical points at x = 1 and x = 2. Which statement correctly classifies them?
- Local maximum at both x = 1 and x = 2
- Local minimum at x = 1, local maximum at x = 2
- Local maximum at x = 1, local minimum at x = 2 Correct answer.
- Local minimum at both x = 1 and x = 2
Explanation
Here f′(x) = 6x² − 18x + 12 and f″(x) = 12x − 18. At x = 1, f″ = −6 < 0, a local maximum; at x = 2, f″ = 6 > 0, a local minimum.
Question 42Applications of Derivatives
Find the point of inflection of the curve y = x³ − 6x² + 5x.
- (0, 0)
- (3, −6)
- (1, 0)
- (2, −6) Correct answer.
Explanation
y′ = 3x² − 12x + 5 and y″ = 6x − 12. Setting y″ = 0 gives x = 2, and substituting gives y = 8 − 24 + 10 = −6, so the inflection point is (2, −6).
Question 43Applications of Derivatives
A rectangular garden is to be fenced on all four sides using 40 m of fencing. What is the maximum possible area?
- 100 m² Correct answer.
- 400 m²
- 80 m²
- 160 m²
Explanation
Let the sides be x and y with 2x + 2y = 40, so y = 20 − x. Area A = x(20 − x) = 20x − x², and A′ = 20 − 2x = 0 gives x = 10. Then y = 10 and the maximum area is 100 m².
Question 44Applications of Derivatives
For what values of x is f(x) = x³ − 3x strictly decreasing?
- x < −1 or x > 1
- −1 < x < 1 Correct answer.
- x < 0
- x > 0
Explanation
f′(x) = 3x² − 3 = 3(x − 1)(x + 1), which is negative between the roots −1 and 1. Hence f is strictly decreasing on (−1, 1).
Question 45Applications of Derivatives
The volume of a sphere increases at 36π cm³/s. At what rate is the radius increasing when r = 3 cm?
- 3 cm/s
- 2 cm/s
- 1 cm/s Correct answer.
- 4 cm/s
Explanation
V = (4/3)πr³, so dV/dt = 4πr² · dr/dt. Substituting dV/dt = 36π and r = 3 gives 36π = 36π · dr/dt, hence dr/dt = 1 cm/s.
Question 46Applications of Derivatives
Using differentials, find the approximate value of √(36.6).
- 6.01
- 6.60
- 6.10
- 6.05 Correct answer.
Explanation
Take f(x) = √x with a = 36 and dx = 0.6. Then f′(x) = 1/(2√x) gives f′(36) = 1/12, so dy ≈ (1/12)(0.6) = 0.05 and √36.6 ≈ 6 + 0.05 = 6.05.
Question 47Applications of Derivatives
Evaluate lim(x→∞) (3x² + 2x + 1)/(x² − 5x + 4).
- 3 Correct answer.
- 0
- ∞
- 1
Explanation
This is of the form ∞/∞, so l'Hôpital's rule applies, or divide numerator and denominator by x². Either way the limit equals the ratio of leading coefficients, 3/1 = 3.
Question 48Applications of Derivatives
A function f satisfies f′(x) = (x − 1)²(x − 3). Which of the following correctly describes the behaviour at x = 1 and x = 3?
- No extremum at x = 1; local maximum at x = 3 Correct answer.
- Local minimum at x = 1; local maximum at x = 3
- Local maximum at x = 1; local minimum at x = 3
- No extremum at either point
Explanation
At x = 1 the factor (x − 1)² does not change sign, so f′ keeps the same sign and there is no extremum (a stationary inflection). At x = 3 the factor (x − 3) changes sign from negative to positive, giving a local maximum as f′ goes from negative to positive.
Question 49Applications of Derivatives
A cone has height 12 cm and base radius 6 cm, with water flowing in at 8 cm³/s. How fast is the water level rising when the depth is 4 cm?
- 2/(3π) cm/s Correct answer.
- 3/(2π) cm/s
- 8/(9π) cm/s
- 1/(3π) cm/s
Explanation
By similar triangles the water radius is r = h/2, so V = (1/3)π(h/2)²h = πh³/12. Then dV/dt = (πh²/4) dh/dt, and at h = 4 this gives 8 = 4π · dh/dt, so dh/dt = 2/(3π) cm/s.
Question 50Applications of Derivatives
The sum of two positive numbers is 20. What is the minimum value of the sum of their squares?
- 400
- 180
- 200 Correct answer.
- 100
Explanation
Let the numbers be x and 20 − x. Then S = x² + (20 − x)² = 2x² − 40x + 400, and S′ = 4x − 40 = 0 gives x = 10. The minimum sum of squares is 10² + 10² = 200.