Limits and Derivatives Exercise 1
Question:
If the functionf(x) satisfies lim(x→1) (f(x)−2)/(x^2−1)=π evaluate lim(x→1)f(x)
Answer:
Step 1: Substitute x = 1 in the equation lim(x→1) (f(x)−2)/(x^2−1)=π
lim(x→1) (f(1)−2)/(1^2−1)=π
Step 2: Solve the equation lim(x→1) (f(1)−2)/(1^2−1)=π
f(1)−2=π
f(1)=2+π
Step 3: Substitute x = 1 in the original equation lim(x→1)f(x) = lim(x→1)(2+π) = 2+π
Question:
Evaluate the given limit: lim(x→0)xsecx
Answer:
Step 1: Rewrite the expression using the definition of secant: lim(x→0)xsecx = lim(x→0)x(1/cosx)
Step 2: Rewrite the expression using the limit definition of cosine: lim(x→0)x(1/cosx) = lim(x→0)x(1/lim(x→0)cosx)
Step 3: Evaluate the limit: lim(x→0)x(1/lim(x→0)cosx) = 0/1 = 0
Question:
Evaluate the limit: lim(x→0)(sin ax+bx)/(ax+sin bx) a,b,a+b≠0
Answer:
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Split the fraction into two parts: lim(x→0)sin ax/ax and lim(x→0)bx/sin bx.
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Apply L’Hopital’s Rule to both parts: lim(x→0)a cos ax/a and lim(x→0)b/cos bx.
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Replace a and b with their respective values: lim(x→0)a cos ax/a = lim(x→0)cos ax and lim(x→0)b/cos bx = lim(x→0)b.
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The limits are equal to 1 and b, respectively.
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Combine the two limits: lim(x→0)(sin ax+bx)/(ax+sin bx) = 1/b.
Question:
Evaluate the Given limit: lim(r→1)πr^2
Answer:
Step 1: Substitute r=1 into the equation: lim(r→1)πr^2 = π1^2 = π
Step 2: Simplify the equation: π1^2 = π
Step 3: The answer is: π
Question:
Evaluate the given limit: lim(x→0)((x+1)^5−1)/x
Answer:
Answer: Step 1: Rewrite the limit as follows: lim(x→0)((x+1)^5−1)/x = lim(x→0)((x+1)^5)/x − lim(x→0)(1)/x
Step 2: Apply L’Hospital’s Rule to both terms: = lim(x→0)(5(x+1)^4)/1 − lim(x→0)(0)/1
Step 3: Simplify both terms: = lim(x→0)(5(x+1)^4) − lim(x→0)(0)
Step 4: Substitute 0 for x in both terms: = 5(0+1)^4 − 0
Step 5: Simplify the expression: = 5(1)^4 − 0
Step 6: Calculate the result: = 5(1) − 0
Step 7: Simplify the expression: = 5 − 0
Step 8: Calculate the result: = 5
Question:
Evaluate the Given limit: lim(x→0)sin ax/bx
Answer:
Step 1: Rewrite the limit as the quotient of two functions: lim(x→0) (sin ax)/(bx)
Step 2: Rewrite the limit using L’Hôpital’s Rule: lim(x→0) (a cos ax)/b
Step 3: Substitute 0 for x in the numerator and denominator: lim(x→0) (a cos 0)/b
Step 4: Simplify the limit: lim(x→0) a/b
Question:
Evaluate the Given limit: lim(x→π)sin(π−x)/π(π−x)
Answer:
Step 1: Rewrite the limit as lim(x→π)sin(x-π)/(x-π).
Step 2: Substitute x=π into the limit.
Step 3: lim(x→π)sin(x-π)/(x-π) = lim(x→π)sin(0)/(0) = 0/0.
Step 4: Apply L’Hospital’s Rule to the limit.
Step 5: lim(x→π)sin(x-π)/(x-π) = lim(x→π)cos(x-π)/1 = lim(x→π)cos(0) = 1.
Question:
Evaluate the Given limit: lim(x→π)(x−22/7)
Answer:
Step 1: Substitute x=π in the given expression, lim(x→π)(x−22/7) = lim(x→π)(π−22/7)
Step 2: Simplify the expression, lim(x→π)(π−22/7) = lim(x→π)(3−22/7)
Step 3: Calculate the limit, lim(x→π)(3−22/7) = 3−22/7 = -1/7
Question:
Evaluate the Given limit: lim(x→0)(ax+b)/(cx+1)
Answer:
Step 1: Substitute x=0 in the given limit.
lim(x→0)(ax+b)/(cx+1) = (a0 + b)/(c0 + 1) = b/1 = b
Step 2: The limit is equal to the value of b.
Answer: lim(x→0)(ax+b)/(cx+1) = b
Question:
Evaluate the Given limit: lim(x→0)(sin ax)/(sin bx),a,b≠0
Answer:
Step 1: Rewrite the given limit as: lim (x→0) (sin ax)/(sin bx)
Step 2: Apply L’Hôpital’s Rule: lim (x→0) (sin ax)/(sin bx) = lim (x→0) (a cos ax)/(b cos bx)
Step 3: Again, apply L’Hôpital’s Rule: lim (x→0) (a cos ax)/(b cos bx) = lim (x→0) (a^2 sin ax)/(b^2 sin bx)
Step 4: Since a and b are non-zero constants, the limit is equal to a^2/b^2.
Therefore, the answer is a^2/b^2.
Question:
Evaluate the Given limit: lim(x→−1)(x^10+x^5+1)/(x−1)
Answer:
Answer: Step 1: Rewrite the given limit in the form of fraction: lim(x→−1) (x^10+x^5+1)/(x−1) = lim(x→−1) (x^10+x^5+1)/x - lim(x→−1) (x^10+x^5+1)/1
Step 2: Apply the Limit Laws: lim(x→−1) (x^10+x^5+1)/x = -∞
Step 3: Apply the Limit Laws: lim(x→−1) (x^10+x^5+1)/1 = -1
Step 4: Subtract the two limits: lim(x→−1) (x^10+x^5+1)/(x−1) = -∞ - (-1)
Step 5: Simplify the result: lim(x→−1) (x^10+x^5+1)/(x−1) = ∞
Question:
Evaluate the given limit: lim(x→0)(cos x)/(π−x)
Answer:
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lim(x→0)(cos x)/(π−x)
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lim(x→0)cos x/(π−x)
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lim(x→0)cos x/π−lim(x→0)x
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1/π−lim(x→0)x/π
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1/π−0
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1/π
Question:
Evaluate: lim(x→3)(4x^2+3)
Answer:
Step 1: Substitute x = 3 into the equation: 4(3)^2 + 3 = 39
Step 2: The limit as x approaches 3 is 39.
Question:
Evaluate the Given limit: lim(x→2) (3x^2−x−10)/(x^2−4)
Answer:
Step 1: Factor the numerator and denominator of the expression:
lim(x→2) (3x^2−x−10)/(x^2−4) = lim(x→2) (3x-5)(x+2)/(x-2)(x+2)
Step 2: Substitute x = 2 in the expression:
lim(x→2) (3x-5)(x+2)/(x-2)(x+2) = (3*2-5)(2+2)/(2-2)(2+2) = (6-5)(4)/(0)(4)
Step 3: Simplify the expression:
(6-5)(4)/(0)(4) = 4/0
Step 4: The limit does not exist as the result is undefined.
Therefore, lim(x→2) (3x^2−x−10)/(x^2−4) = undefined.
Question:
Evaluate the Given limit: lim(x→3)(x+3)
Answer:
Step 1: Substitute x=3 in the limit lim(x→3)(x+3) = 3 + 3 = 6
Step 2: The limit is equal to 6.
Question:
If f(x)=∣x∣−5 , evaluate the following limits: L(x→5)f(x)
Answer:
Answer:
Step 1: Substitute x = 5 in the given function: f(x) = |x| - 5 f(5) = |5| - 5 f(5) = 5 - 5 f(5) = 0
Step 2: Evaluate the limit: L(x→5)f(x) = 0
Question:
Evaluate: lim(x→−2)(1/x+1/2)(x+2)
Answer:
Step 1: Rewrite the expression as: lim(x→−2)(1/x)(x+2) + lim(x→−2)(1/2)(x+2)
Step 2: Substitute -2 for x in each expression: lim(x→−2)(1/x)(x+2) = 1/−2 * −2 + 2 = 0
Step 3: Evaluate the second expression: lim(x→−2)(1/2)(x+2) = 1/2 * −2 + 2 = 1
Step 4: Add the two expressions: 0 + 1 = 1
Therefore, the answer is 1.
Question:
lim(x→0)(cos 2x−1)/(cos x−1)
Answer:
Step 1: Factor out a cos x from the numerator and denominator:
lim(x→0)(cos x(cos x - 2))/(cos x - 1)
Step 2: Use the fact that cos x approaches 1 as x approaches 0:
lim(x→0)(cos x(-2))/(-1)
Step 3: Simplify:
lim(x→0)(-2cos x)/(-1)
Step 4: Factor out a -2 from the numerator and denominator:
lim(x→0)(-2(cos x))/(-2(-1))
Step 5: Simplify:
lim(x→0)(cos x)/(2)
Step 6: The answer is 1/2.
Question:
Evaluate the Given limit: lim(x→3) (x^4−81)/(2x^2−5x−3)
Answer:
Step 1: Rewrite the given expression as: lim(x→3) (x^4−81)/(2x^2−5x−3)
Step 2: Substitute x = 3 in the expression: lim(x→3) (3^4−81)/(2(3)^2−5(3)−3)
Step 3: Simplify the expression: lim(x→3) (81−81)/(18−15−3)
Step 4: Simplify the expression further: lim(x→3) 0/0
Step 5: Apply L’Hospital’s Rule: lim(x→3) (4x^3)/(4x−5)
Step 6: Substitute x = 3 in the expression: lim(x→3) (4(3)^3)/(4(3)−5)
Step 7: Simplify the expression: lim(x→3) 81/7
Step 8: The limit is 81/7.
Question:
lim(z→1) (z^(1/3)−1)/(z^(1/6)−1)
Answer:
Step 1: Simplify the expression by multiplying the numerator and denominator by (z^(1/6) + 1):
lim(z→1) (z^(1/3)−1)/(z^(1/6)−1) * (z^(1/6) + 1)
Step 2: Simplify the expression by factoring the numerator and denominator:
lim(z→1) (z^(1/2) + z^(1/3) - z^(1/6) - 1)/(z^(1/6) - 1)
Step 3: Substitute z = 1 into the expression:
lim(z→1) (1 + 1 - 1 - 1)/(1 - 1)
Step 4: Simplify the expression:
lim(z→1) 0/0
Question:
Evaluate the Given limit: lim(x→1) (ax^2+bx+c)/(cx^2+bx+a),a+b+c≠0
Answer:
Step 1: Substitute x=1 in the given expression: lim(x→1) (ax2+bx+c)/(cx2+bx+a),a+b+c≠0 = (a+b+c)/(c+b+a)
Step 2: Since a+b+c≠0, the given expression is a non-zero constant.
Step 3: Therefore, the limit of the given expression is (a+b+c)/(c+b+a).
Question:
Let a1,a2,…,an be fixed real numbers and define a function f(x)=(x−a1)(x−a2)….(x−an). What is lim(x→a1)f(x)? For some a≠a1,a2,…,an, compute lim(x→a)f(x).
Answer:
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lim(x→a1)f(x)=0
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lim(x→a)f(x)=∏(a−a1)(a−a2)….(a−an)
Question:
Evaluate the given limit: lim(x→0)(ax+x cos x)/(b sinx)
Answer:
Step 1: Rewrite the expression as
lim(x→0)(ax + xcosx)/(bsinx)
Step 2: Simplify the expression by using the properties of limits
lim(x→0)(ax + xcosx)/(bsinx) = lim(x→0)(ax + x(1 - (sinx)^2))/(bsinx)
Step 3: Apply L’Hospital’s Rule
lim(x→0)(ax + x(1 - (sinx)^2))/(bsinx) = lim(x→0)(a + x(-2sinxcosx))/(bcosx)
Step 4: Simplify the expression
lim(x→0)(a + x(-2sinxcosx))/(bcosx) = lim(x→0)(a - 2xsin^2x)/(bcosx)
Step 5: Apply L’Hospital’s Rule
lim(x→0)(a - 2xsin^2x)/(bcosx) = lim(x→0)(-2xcos^2x)/(-bsinx)
Step 6: Simplify the expression
lim(x→0)(-2xcos^2x)/(-bsinx) = lim(x→0)(2xcos^2x)/(bsinx)
Step 7: Apply L’Hospital’s Rule
lim(x→0)(2xcos^2x)/(bsinx) = lim(x→0)(2cos^2x + 2x(-2sinxcosx))/(bcosx)
Step 8: Simplify the expression
lim(x→0)(2cos^2x + 2x(-2sinxcosx))/(bcosx) = lim(x→0)(2cos^2x - 4xsin^2x)/(bcosx)
Step 9: Apply L’Hospital’s Rule
lim(x→0)(2cos^2x - 4xsin^2x)/(bcosx) = lim(x→0)(-4cos^2x - 8xsin^2xcosx)/(-bsinx)
Step 10: Simplify the expression
lim(x→0)(-4cos^2x - 8xsin^2xcosx)/(-bsinx) = lim(x→0)(4cos^2x + 8xsin^2xcosx)/(bsinx)
Step 11: Substitute x = 0
lim(x→0)(4cos^2x + 8xsin^2xcosx)/(bsinx) = 4/b
Question:
Solve: lim(x→0)(cosecx−cotx)
Answer:
Step 1: Rewrite cosecx and cotx using their definitions:
lim(x→0)(1/sinx−1/tanx)
Step 2: Use L’Hôpital’s rule:
lim(x→0)(-cosx/sinx^2−sec^2x/cosx)
Step 3: Simplify:
lim(x→0)(-1/sinx−sec^2x)
Step 4: Evaluate the limit:
lim(x→0)(-1/0−1/1)
Step 5: Answer: -1