Question

how would you find the value of cos (-15)

Answer 1

Go to calculator, and press cos then enter -15) XD

Answer 2

-0.75968791285

Answer 3

.9659258269

Answer 4

@ColourThesis use sum and difference identities not calculator

Answer 5

As cosine is an even function

cos (-15)=cos (15)

Now cos(15) can be written as
cos (30/2)=\(\sqrt{\dfrac{1+\cos 30}{2}}\)

Answer 6

I hope you can do it from there.

Answer 7

@AravindG but my prof wanted me to find cos(-15) using sum and difference so how am i going to do that?

Answer 8

ur Prof is mean lol

Answer 9

here: http://home.windstream.net/okrebs/page101.html my prof recommended this website when we were learning this