How do you solve a triangle given a = 8, c = 12, and B = 72?

1 Answer
Nov 8, 2015

Law of sine and cosine


You first need to fine the missing side, in this case it would be 'b.'

Use this equation: #b^2=a^2+c^2-2acsinb#

You will have the side b and can use the the same equation, just manipulated to find the other angle.

That equation is: #(-a^2+b^2+c^2)/(2bc)=sinA#

That will give you the angle of angle A. Since you have 2 angles of the triangle you can easily find the third, simply subtracting the sum of both angles from 180.