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Math

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PROBLEM

Consider the limit
limx0sin2(8x)1cos(8x)\lim _{x \rightarrow 0} \frac{\sin ^{2}(8 x)}{1-\cos (8 x)} To simplify this limit, we should multiply numerator and denominator by the expression
\square
After doing this and simplifying the result we find that the value of limit is
\square
Note: You can earn partial credit on this problem.
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STEP 1

1. The limit involves trigonometric functions and requires simplification.
2. The expression sin2(8x)1cos(8x) \frac{\sin^2(8x)}{1-\cos(8x)} can be simplified using trigonometric identities.
3. Multiplying by a conjugate can help simplify the expression.

STEP 2

1. Identify the conjugate to multiply the expression.
2. Simplify the expression using trigonometric identities.
3. Evaluate the limit.

STEP 3

To simplify the expression, multiply the numerator and denominator by the conjugate of the denominator. The conjugate of 1cos(8x) 1 - \cos(8x) is 1+cos(8x) 1 + \cos(8x) . Therefore, multiply by:
1+cos(8x)1+cos(8x) \frac{1 + \cos(8x)}{1 + \cos(8x)}

STEP 4

Simplify the expression after multiplying by the conjugate:
sin2(8x)(1+cos(8x))(1cos(8x))(1+cos(8x)) \frac{\sin^2(8x)(1 + \cos(8x))}{(1 - \cos(8x))(1 + \cos(8x))} The denominator becomes:
(1cos(8x))(1+cos(8x))=1cos2(8x)=sin2(8x) (1 - \cos(8x))(1 + \cos(8x)) = 1 - \cos^2(8x) = \sin^2(8x) So the expression simplifies to:
sin2(8x)(1+cos(8x))sin2(8x) \frac{\sin^2(8x)(1 + \cos(8x))}{\sin^2(8x)} Cancel sin2(8x)\sin^2(8x) from the numerator and denominator:
1+cos(8x) 1 + \cos(8x)

SOLUTION

Now evaluate the limit as x0 x \rightarrow 0 :
limx0(1+cos(8x)) \lim_{x \rightarrow 0} (1 + \cos(8x)) Since cos(8x)\cos(8x) approaches cos(0)=1\cos(0) = 1 as x0 x \rightarrow 0 , the limit is:
1+1=2 1 + 1 = 2 The expression to multiply by is:
1+cos(8x) \boxed{1 + \cos(8x)} The value of the limit is:
2 \boxed{2}

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