Cos a = 0.83 and cos b = 0.55. what is sin a + sin b?

If the cos A = .83 then the arc cosine of .83 equals the angle
arc cosine (.83) = 33.901 degrees
Similarly, we look up the arc cosine of .55
arc cosine (.55) = 56.633 degrees

NOW we can look up the sine of 33.901 degrees and find it is the
sine of A and it equals 0.55776

the sine of 56.633 degrees = 0.83516 and that is the sine of B

Just divide the x axis (the top) by 2 or multiply the y axis (the bottom) by 2