Which of these is equal to cos 47°?

A)

cos 43°

B)

sin 43°

C)

tan 43°

D)

cos 133°

Surely this is a trick question, none of the aforementioned values are equal to cos (47).

For sine and cosine angles, it is said that sine/cosine angles are equal to their supplementary angles. Supplementary angles are those angles, that when added to the original angle, would be equal to 180.

In the case of cos 47, getting the supplementary angle would mean subtracting 47 from 180. To show this:

180 - 47 = 133

Therefore cos 47 = cos 133