You're on a roll — here are the solutions for these limit problems.
1. Evaluate: limx→0xsinx
Step 1: This is a fundamental trigonometric limit.
limx→0xsinx=1
The limit is 1.
2. Evaluate: limx→0x21−cosx
Step 1: This is a fundamental trigonometric limit.
limx→0x21−cosx=21
The limit is 21.
3. Evaluate: limx→∞xlnx
Step 1: As x→∞, both lnx→∞ and x→∞, which is an indeterminate form ∞∞. Apply L'Hôpital's Rule.
limx→∞xlnx=limx→∞dxd(x)dxd(lnx)
Step 2: Differentiate the numerator and the denominator.
limx→∞1x1=limx→∞x1
Step 3: Evaluate the limit.
limx→∞x1=0
The limit is 0.
4. Evaluate: limx→∞exx
Step 1: As x→∞, both x→∞ and ex→∞, which is an indeterminate form ∞∞. Apply L'Hôpital's Rule.
limx→∞exx=limx→∞dxd(ex)dxd(x)
Step 2: Differentiate the numerator and the denominator.
limx→∞ex1
Step 3: Evaluate the limit. As x→∞, ex→∞, so ex1→0.
limx→∞ex1=0
The limit is 0.
5. Evaluate: limx→0xex−1
Step 1: This is a fundamental limit related to the exponential function.
limx→0xex−1=1
The limit is 1.
6. Evaluate: limx→1x−1lnx
Step 1: As x→1, lnx→ln1=0 and x−1→1−1=0, which is an indeterminate form 00. Apply L'Hôpital's Rule.
limx→1x−1lnx=limx→1dxd(x−1)dxd(lnx)
Step 2: Differentiate the numerator and the denominator.
limx→11x1=limx→1x1
Step 3: Substitute x=1 into the expression.
limx→1x1=11=1
The limit is 1.
7. Evaluate: limx→0x3tanx−x
Step 1: As x→0, tanx−x→0−0=0 and x3→0, which is an indeterminate form 00. Apply L'Hôpital's Rule.
limx→0x3tanx−x=limx→03x2sec2x−1
Step 2: This is still an indeterminate form 00 since sec20−1=1−1=0. Apply L'Hôpital's Rule again.
limx→03x2sec2x−1=limx→06x2secx(secxtanx)=limx→06x2sec2xtanx=limx→03xsec2xtanx
Step 3: This is still an indeterminate form 00. Apply L'Hôpital's Rule a third time.
limx→03xsec2xtanx=limx→03(2secx(secxtanx))tanx+sec2x(sec2x)
=limx→032sec2xtan2x+sec4x
Step 4: Substitute x=0.
32sec20tan20+sec40=32(1)2(0)2+(1)4=30+1=31
The limit is 31.
8. Evaluate: limx→∞exx2+1
Step 1: As x→∞, both x2+1→∞ and ex→∞, which is an indeterminate form ∞∞. Apply L'Hôpital's Rule.
limx→∞exx2+1=limx→∞dxd(ex)dxd(x2+1)=limx→∞ex2x
Step 2: This is still an indeterminate form ∞∞. Apply L'Hôpital's Rule again.
limx→∞ex2x=limx→∞dxd(ex)dxd(2x)=limx→∞ex2
Step 3: Evaluate the limit. As x→∞, ex→∞, so ex2→0.
limx→∞ex2=0
The limit is 0.
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