PROBLEM
18. [-/1 Points]
DETAILS
MY NOTES
SCALCET9M 4.4.058.
ASK YOL
Find the limit. Use I'Hospital's Rule where appropriate. If there is a more elementary method, consider using it.
x→0+lim(tan(8x))x □
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STEP 1
Assumptions
1. We need to find the limit: x→0+lim(tan(8x))x 2. The function is in the indeterminate form 00 as x→0+.
3. We will use logarithmic properties and L'Hospital's Rule to solve this limit.
STEP 2
To handle the indeterminate form 00, take the natural logarithm of the function. Let y=(tan(8x))x, then:
lny=xln(tan(8x))
STEP 3
Now, find the limit of lny as x→0+:
x→0+limlny=x→0+limxln(tan(8x))
STEP 4
This limit is in the form 0⋅(−∞), which is indeterminate. Rewrite it as a fraction:
x→0+limxln(tan(8x))=x→0+lim1/xln(tan(8x))
STEP 5
Now, the limit is in the form ∞−∞, which is suitable for L'Hospital's Rule. Differentiate the numerator and the denominator:
Numerator: dxd[ln(tan(8x))]=tan(8x)1⋅sec2(8x)⋅8=tan(8x)8sec2(8x)
Denominator: dxd[1/x]=−x21
STEP 6
Apply L'Hospital's Rule:
x→0+lim1/xln(tan(8x))=x→0+limtan(8x)8sec2(8x)⋅(−x2)
STEP 7
Simplify the expression:
=x→0+lim−8x2⋅tan(8x)sec2(8x)
STEP 8
As x→0+, tan(8x)≈8x and sec2(8x)≈1. Substitute these approximations:
=x→0+lim−8x2⋅8x1
STEP 9
Simplify further:
=x→0+lim−x
STEP 10
Evaluate the limit:
=0
STEP 11
Since limx→0+lny=0, we have lny=0, which implies y=e0=1.
SOLUTION
Thus, the original limit is:
x→0+lim(tan(8x))x=1
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