SOLUTION: In a triangle ABC, angle A = 2 angle B. How would you prove that BC² = AC² + AB × AC?

Algebra ->  Triangles -> SOLUTION: In a triangle ABC, angle A = 2 angle B. How would you prove that BC² = AC² + AB × AC?      Log On


   

Question 1035292: In a triangle ABC, angle A = 2 angle B. How would you prove that BC² = AC² + AB × AC?
Answer by richard1234(7193) About Me  (Show Source):
You can put this solution on YOUR website!
Use law of sines. Here .



Cross-multiplying, this is equivalent to .

Applying the law of cosines, we have



This is equivalent to .

Substituting we have



You can then solve for . However I don't think what I got matches with the expression you provided (either I messed up my algebra or the question you typed is incorrect).