Given a triangle with b=4, c=10, and A=84*, what is the length of a? Round to the nearest tenth. I know you have to use the law of cosines, but i am really confused on how to do this.

We are given with two sides b=4, c=10 and an angle of 84 degrees. Using cosine law to determine the third side, we use the formula:

a^2 = b^2 + c^2 - 2bc cos thetaa^2 = 4^2 + 10^2 - 2*4*10 cos 84a^2 = 107.64a = 10. 37 units