Need help ............?

Question

cos A = .7986, find angle A.

tan R = 4.0108, find angle R.

Answer 1

When you have an equation like 2x = 8 you solve it by dividing both sides by 2 because dividing by 2 undoes the multiplication by 2 since 2x/2 = x.  

Similarly, when you have an equation

cos(A) = .7986

you solve it by taking the arccos of both sides since arccos(cos(A)) = A.  By the way, arccos(x) is also written as cos^(-1)(x).  

arccos(cos(A)) = arccos(.7986)

A = arccos(.7986)

A = 37º (approx)

tan(R) = 4.0108

arctan(tan(R)) = arctan(4.0108)

R = arctan(4.0108)

R = 76º (approx)

Hope this helps you!