cos 80 degrees=

Sine, Cosine and Tangent are all based on a Right-Angled Triangle

There are 4 quadrants in a central circle

The angle lies in the first quadrant based on the number of degrees of the central circle which means the answer will be positive

I 0°<X<90°

This is for degrees not radians

If using your calculator make sure the calculator is set for degrees and not radians (it should say DEG at the top)

Input 80

push "COS)

and you will get .17

ifyou get -o.11 then your calculator is set for radians which would be incorrect because you are asked for the cos of degrees.

Calculation is:

=sin(pi/18)

=.17