Larry S. answered 04/22/20
Mechanical Design Engineer & Certified SolidWorks Professional
You need to pick at least 5 identities and replace the angle value of -5 degrees and solve for the other angle.
For instance, sin (-theta)= - sin(theta) or the sine of the negative angle = the negative of the sine of the same positive angle, so,
sin (5 deg)=.0872, which was given, so -.0872 = sin(-5 deg), which means that by knowing the sine of 5 degrees, you also know the sine of negative 5 degrees.
From the Pythagorean theorem, sin2 (theta)+ cos2 (theta)= 1 so cos(5 deg) = square root of (1 - sin2 (5 deg)) = square root of (1 -(.0872)^2) = sqrt (.99239616) = .9962, so you now also know the cosine of 5 degrees.