Question

Which of the following is a trigonometric identity?

Answer 1

Your idea?

Answer 2

I only know the early basics on these expressions. Im pretty sure A) and B) are not correct. Im not sure.

Answer 3

Yes, you are correct, It is not A nor B. How about C or D?
what I concern is how to show you the expression is NOT identity. However, it can be proved ( just take time).
forget proving. now, consider C and D
C first

Answer 4

Hint: the right hand side: 1-2sin^2 = 1-sin^2 -sin^2
cancel out with the left hand side. you can see ..."something"

Answer 5

C is a correct as it is. Does that make it the trig identity?

Answer 6

yup

Answer 7

thank you ^_^

Answer 8

np