Question

Without using a calculator, find the exact value of cos^-1(cos(17pi/5)). Justify your answer

Answer 1

without using calculator can u tell the exact value of below expression ? :-

\(\large 9876 \times \frac{1}{9876} \pi\)

Answer 2

isn't that just pi because both 9876 cancel each other ?

Answer 3

$$\large \text{Note:} \cos^{-1}(\cos x)= x$$

Answer 4

true, they cance out cuz division is inverse of multiplication

similarly cos^-1 is inverse of cos, so.. ?

Answer 5

*cancel

Answer 6

`"x" here will be exact `

Answer 7

so they will cancel too and it will become x ??

Answer 8

or will the answer just be 17pi/5 ?

Answer 9

\(cos^-1(cos(17\pi/5)) \)

\(\cancel{cos^-1}\cancel{cos}(17\pi/5) \)

\(17\pi/5\)

Answer 10

yes !

Answer 11

thanks ! :)

Answer 12

np, keep in mind, u need to be bit careful if x is negative.