SOLUTION: is PQ=25, QR=20 and PR=23, which angle in the triangle is the largest?

Algebra ->  Triangles -> SOLUTION: is PQ=25, QR=20 and PR=23, which angle in the triangle is the largest?      Log On


   

Question 389063: is PQ=25, QR=20 and PR=23, which angle in the triangle is the largest?
Answer by Fombitz(32388) About Me  (Show Source):
You can put this solution on YOUR website!
From the law of cosines,
PQ%5E2=QR%5E2%2BPR%5E2-2%28QR%29%28PR%29cos%28R%29
cos%28R%29=%28QR%5E2%2BPR%5E2-PQ%5E2%29%2F%282%28QR%29%28PR%29%29
cos%28R%29=%2820%5E2%2B23%5E2-25%5E2%29%2F%282%2820%29%2823%29%29
cos%28R%29=304%2F920
cos%28R%29=0.3304
highlight%28R=70.7%29 degrees