cos 23pi/12

i tried doing it and i got 0.994.. is that right? can someone explain how to do this to me? thanks!

2 answers

it's to find the exact value..sorry i didn't mentioned before and thanks
cos 23pi/12 = cos (2pi - pi/12) = cos pi/12

4th quadrant

cos pi/12 = cos [(pi/6)/2] = sqrt((1 + cos pi/6)/2)
= sqrt((1+√3/2)/2)
= 0.9659

You could have used any good calculator to see whether your answer was right. 23pi/12 = -15 degrees