Solve the triangle. A = 21°, C = 105°, c = 5

You're going to use the Law of Sines here for this. But first we can find the missing angle by adding up the angles we know and subtracting that from 180. So 180 - (21 + 105) = 54. So we have all the angles. Now use the Law of Sines to find the missing side a first. Set it up like this: a/Sin (21) = 5/Sin (105). Multiply both sides by sin (21) to get a = 5sin (21) / sin (105). Now just enter this into your calculator and hit enter. Make sure your calculator is in degree mode when you do this. We will find that the length of a is 1.86. Now do the same to find side b: b/sin (54) = 5/sin (105). Can you handle that one on your own?