Question

Help needed. The problem is in the attachment.

Answer 1

here is the problem.

Answer 2

what is this problem from?

Answer 3

it's in webassign

Answer 4

please help me answer this problem

Answer 5

you have to find 'a' right..?

Answer 6

you have to solve the equation for "a"
\[ 4300 = 7920 \cdot \cos^{-1}\left(\frac{3960}{a+3960}\right) \]

divide both sides by 7920

\[ \frac{4300} {7920 }= \cos^{-1}\left(\frac{3960}{a+3960}\right) \]

take the cosine of both sides. This "undoes" the inverse cos on the right side
\[\cos\left( \frac{4300} {7920 }\right) = \frac{3960}{a+3960} \]

now the only trick, is that you must be in *radian* mode when you take the cosine of the left side.

can you finish ?

Answer 7

i've finished solving it. The answer is 665.25. is it correct sir?

Answer 8

I got 665.09 which is close enough.