13 Limits and Derivatives
Exercise 2
Question:
Find the derivative of the following: (5x^3+3x−1)(x−1).
Answer:
(5x^3+3x−1)(x−1)
= (5x^3+3x−1)(1) + (5x^3+3x−1)(-1)
= (5x^3+3x−1) + (-5x^3-3x+1)
= 0 + 0
= 0
Derivative of (5x^3+3x−1)(x−1) = 0
Question:
Find the derivative of the following: x^(−4)(3−4x^(−5)).
Answer:
Step 1: Use the power rule to rewrite the expression as: x^(-4 + (-5))(3 - 4x^(-5))
Step 2: Apply the power rule to the first term: (-4 + (-5))x^(-9)
Step 3: Apply the power rule to the second term: -4(-5)x^(-6)
Step 4: Combine the results: (-9)x^(-9) - 4(-5)x^(-6)
Step 5: Simplify: -9x^(-9) + 20x^(-6)
Question:
Find the derivative of the following functions:2tanx−7secx
Answer:
-
Use the Chain Rule: d/dx[2tanx - 7secx] = (2)(sec^2x) - (7)(secxtanx)
-
Simplify: (2)(sec^2x) - (7)(secxtanx) = 2sec^2x - 7sec^2x = -5sec^2x
Question:
Find the derivative of x at x=1
Answer:
Step 1: Begin with the equation for the derivative of a function f(x): f’(x) = lim (h→0) (f(x+h) - f(x))/h
Step 2: Substitute x=1 into the equation for the derivative of a function f(x): f’(1) = lim (h→0) (f(1+h) - f(1))/h
Step 3: Evaluate the limit as h approaches 0: f’(1) = lim (h→0) ((1+h) - 1)/h
Step 4: Simplify the equation: f’(1) = lim (h→0) (h/h)
Step 5: Evaluate the limit as h approaches 0: f’(1) = lim (h→0) 1
Step 6: The answer is: f’(1) = 1
Question:
For some constant a and b, find the derivative of the following functions: (ax^2+b)^2.
Answer:
Answer: Step 1: Use the power rule to find the derivative of (ax^2+b)^2.
Derivative = 2(ax^2+b)^2 * (2ax)
Step 2: Simplify the expression.
Derivative = 4a(ax^2+b)^2x
Question:
Find the derivatives of the following: secx.
Answer:
-
Use the chain rule: dy/dx = dy/du * du/dx
-
Identify the function: y = secx
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Identify the derivative of the inner function: du/dx = tanx
-
Substitute into the chain rule: dy/dx = secx * tanx
-
Simplify: dy/dx = secxtanx
Question:
Find the derivative of the following functions: sin x cos x
Answer:
-
Use the product rule: d/dx (sin x cos x) = (d/dx sin x) cos x + (d/dx cos x) sin x
-
Use the chain rule: d/dx (sin x cos x) = (cos x)(d/dx sin x) + (sin x)(d/dx cos x)
-
Use the derivatives of sin x and cos x: d/dx (sin x cos x) = (cos x)(cos x) + (sin x)(-sin x)
-
Simplify: d/dx (sin x cos x) = cos2x - sin2x
Question:
Find the derivative of x^(−3)(5+3x)
Answer:
Answer: Step 1: Take the natural log of both sides: ln(x^(-3)(5+3x))
Step 2: Use the product rule to take the derivative: (-3x^(-4))(5+3x) + x^(-3)(3)
Step 3: Simplify: -3x^(-4)(5+3x) + 3x^(-3)
Step 4: Simplify further: -15x^(-4) + 3x^(-3)
Question:
Find the derivative of the following functions: 5secx+4cosx
Answer:
Answer: Step 1: Take the derivative of 5secx Derivative of 5secx = 5secx tanx
Step 2: Take the derivative of 4cosx Derivative of 4cosx = -4sinx
Step 3: Combine the derivatives Derivative of 5secx + 4cosx = 5secx tanx - 4sinx
Question:
Find the derivative of the following functions from first principle x^3−27
Answer:
Answer: Step 1: Identify the given function as f(x) = x^3 − 27
Step 2: Take the derivative of the function using the first principle, i.e., using the power rule
d/dx (f(x)) = d/dx (x^3 − 27)
Step 3: Apply the power rule:
d/dx (x^3 − 27) = 3x^2 (derivative of x^3) − 0 (derivative of 27)
Step 4: Simplify the expression:
d/dx (x^3 − 27) = 3x^2
Therefore, the derivative of the given function f(x) = x^3 − 27 is 3x^2.
Question:
For any constant real number a, find the derivative of: x^n+ax^(n−1)+a^2x^(n−2)+…+a^(n−1)x+a^n.
Answer:
Answer: Step 1: Use the power rule of derivatives to find the derivative of each term:
d/dx[x^n] = nx^(n-1)
d/dx[ax^(n-1)] = (n-1)ax^(n-2)
d/dx[a^2x^(n-2)] = (n-2)a^2x^(n-3)
d/dx[a^(n-1)x] = (n-1)a^(n-1)
d/dx[a^n] = 0
Step 2: Combine the derivatives to get the derivative of the entire expression:
d/dx[x^n+ax^(n−1)+a^2x^(n−2)+…+a^(n−1)x+a^n] = nx^(n-1) + (n-1)ax^(n-2) + (n-2)a^2x^(n-3) + … + (n-1)a^(n-1)
Question:
Find the derivative of the following functions: cosecx
Answer:
Answer: Step 1: Use the chain rule to rewrite the function as: cosecx = 1/sinx
Step 2: Take the derivative of 1/sinx using the quotient rule: d/dx (1/sinx) = -cosx/sinx^2
Step 3: Rewrite the expression using the cosecant function: d/dx (cosecx) = -cosecx * cotx
Question:
Find the derivative of x^2 - 2 at x = 10
Answer:
-
Identify the function: x^2 - 2
-
Take the derivative of the function: 2x
-
Substitute x = 10 into the derivative: 2(10) = 20
Question:
If f(x)=x^100/100+x^99/99+x^98/98 +…+x+1,showthatf’(1)=100 f’(0)$$.
Answer:
f’(x) = 100x^99/100 + 99x^98/99 + 98x^97/98 + … + 1
f’(1) = 100x^99/100 + 99x^98/99 + 98x^97/98 + … + 1
f’(1) = 100
f’(0) = 0x^99/100 + 99x^98/99 + 98x^97/98 + … + 1
f’(0) = 1
Question:
For some constant a and b, find the derivative of the following functions: (x−a)(x−b).
Answer:
Answer: Step 1: Rewrite the function as: (x-a)(x-b) = x^2 - (a+b)x + ab
Step 2: Take the derivative of the function: 2x - (a+b)
Step 3: Simplify the derivative: 2x - (a+b) = 2x - a - b
Question:
Find the derivatives of the following: 5sinx−6cosx+7.
Answer:
Answer:
-
Use the Chain Rule: d/dx[5sinx−6cosx+7] = d/dx[5sinx] - d/dx[6cosx] + d/dx[7]
-
Use the derivatives of sine and cosine: d/dx[5sinx] = 5cosx d/dx[6cosx] = -6sinx d/dx[7] = 0
-
Substitute the derivatives into the original equation: d/dx[5sinx−6cosx+7] = 5cosx - 6sinx + 0
-
Simplify: d/dx[5sinx−6cosx+7] = 5cosx - 6sinx
Question:
Find the derivative of 2x−3/4
Answer:
Answer:
- Rewrite the expression in terms of a fraction: (2x - 3)/4
- Take the derivative of numerator and denominator separately: Numerator: 2 Denominator: 0
- Combine the two derivatives: 2/0
- Simplify: Undefined
Question:
For some constant a and b, find the derivative of the following functions: (x−a)/(x−b).
Answer:
Answer: Step 1: Rewrite the function as: (x - a)(x - b)^-1
Step 2: Use the power rule to take the derivative of the function: -1(x - a)(x - b)^-2 + (x - b)^-1
Step 3: Simplify the derivative: (b - a)(x - b)^-2
Question:
Find the derivative of the following: x^5(3−6x^(−9)).
Answer:
Step 1: Rewrite the expression as x^14 - 6x^5.
Step 2: Use the power rule to find the derivative.
Step 3: The derivative of x^14 is 14x^13.
Step 4: The derivative of -6x^5 is -30x^4.
Step 5: Combine the two derivatives to get the final answer: 14x^13 - 30x^4.
Question:
Find the derivative of
Answer:
y = x^2
-
Rewrite the equation as y’ = (x^2)'
-
Apply the power rule: (x^2)’ = 2x^(2-1)
-
Simplify: (x^2)’ = 2x^1
-
Rewrite the equation as y’ = 2x
Question:
2/(x+1)−x^2/(3x−1)
Answer:
- Simplify the left side: 2/(x+1)
- Simplify the right side: -x^2/(3x-1)
- Combine the two sides: 2/(x+1) - (-x^2/(3x-1))
- Combine the denominators: (3x-1)(x+1)
- Multiply both sides by the denominator: (3x-1)(x+1) [2/(x+1) - (-x^2/(3x-1))]
- Simplify the left side: (3x-1) + (2x^2)
- Simplify the right side: -x^3 - 2
- Combine the two sides: (3x-1) + (2x^2) - (-x^3 - 2)
- Combine like terms: 3x-1 + 2x^2 + x^3 + 2
- Simplify: 4x^3 + 3x - 1
Question:
Find the derivative of cosx by first principle.
Answer:
Answer: Step 1: Let y = cosx
Step 2: Calculate the derivative of y with respect to x using the first principle:
d/dx(y) = limh→0 (y + h - y) / h
Step 3: Substitute y = cosx into the equation:
d/dx(cosx) = limh→0 (cosx + h - cosx) / h
Step 4: Simplify the equation:
d/dx(cosx) = limh→0 (h) / h
Step 5: The limit of h as it approaches 0 is 0, so the equation becomes:
d/dx(cosx) = 0
Question:
Find the derivative of 99x at x=100
Answer:
Answer: Step 1: Rewrite the equation as y = 99x
Step 2: Take the derivative of y with respect to x: dy/dx = 99
Step 3: Evaluate the derivative at x=100: dy/dx = 99(100) = 9900
Question:
Find the derivatives of the following: 3cotx+5cosecx.
Answer:
Answer:
Step 1: Use the chain rule to find the derivative of 3cotx.
d/dx (3cotx) = -3csc2x
Step 2: Use the chain rule to find the derivative of 5cosecx.
d/dx (5cosecx) = 5cosecxcotx
Therefore, the derivatives of 3cotx+5cosecx is -3csc2x + 5cosecxcotx.
Question:
Find the derivative of (x^n−a^n)/(x−a) for some constant a
Answer:
Answer:
-
Rewrite the given expression as: (x^n - a^n)/(x - a)
-
Apply the quotient rule for derivatives: n*(x^(n-1))(x - a) - n(a^(n-1))/(x - a)^2
-
Simplify the fraction: n*(x^(n-1)) - n*(a^(n-1))/(x - a)
-
Factor out the common terms: n*(x^(n-1) - a^(n-1))/(x - a)
JEE NCERT Solutions (Mathematics)
01 Sets
02 Relations and Functions
03 Trigonometric Functions
04 Principle of Mathematical Induction
05 Complex Numbers and Quadratic Equations
06 Linear Inequalities
07 Permutations and Combinations
08 Binomial Theorem
09 Sequences and Series
10 Straight Lines Exercise
10 Straight Lines Miscellaneous
11 Conic Sections
12 Introduction to Three Dimensional Geometry
13 Limits and Derivatives
14 Mathematical Reasoning
15 Statistics
16 Probability