# The Cosine Curve - cos 20, cos 85

Trigonometry equalities, inequalities and expressions - sin, cos, tan, cot

### The Cosine Curve - cos 20, cos 85

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!
Guest

### Re: The Cosine Curve

cos 60 = cos 3*20
and we can use this formula:
Guest

### Re: The Cosine Curve

I will continue thinking and I will write later.
Guest

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