Question

How do you find the exact value of the following using the unit circle sec (-3 pi/ 4)?

Answer 1

`- sqrt2`

Explanation:

`sec ((-3pi)/4) = 1/(cos)`
First, find `cos ((-3pi)/4)`.
Trig table of special arcs and unit circle -->
`cos ((-3pi)/4) = cos (pi/4 - (4pi)/4) = cos (pi/4 + pi) =`
`= -cos (pi/4) = - sqrt2/2`
There for:
`sec ((-3pi)/4) = 1/(cos) = - 2/sqrt2 = - sqrt2`