Question

Use a double-angle identity to find the exact value of the trigonometric expression.

cos 420°

Answer 1

You can always use a double-angle identity for something.
Here it is simple enough to use
cos(420)=cos(420-360)=cos(60)=1/2

Answer 2

one to go

Answer 3

Thanks!

Answer 4

@EmilyJernigan i told you wrong last time
it should have been positive, not negative
sorry
if you can change it, do

Answer 5

Its fine. Thats what i thought!