1. ## The Cosine Curve

Hi there I would like to know how to do the following questions without drawing a graph. What is the formula?

The question: Express each of the following in terms of the cosine of another angle between 0° and 180°

a) cos 20°
b) cos 85°

Thank you for any help!

2. Originally Posted by Xine

What is the formula?

There is no formula.

Treat the given angles as reference angles or use the symmetry of a unit circle.

If you have not been taught either of these concepts, let us know.

Cheers ~ Mark

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