SOLUTION: Triangle ABC has side a = 11, b = 14 and c = 17. Find the measure of angle A to the nearest whole number.

Algebra ->  Triangles -> SOLUTION: Triangle ABC has side a = 11, b = 14 and c = 17. Find the measure of angle A to the nearest whole number.      Log On


   

Question 999906: Triangle ABC has side a = 11, b = 14
and c = 17.
Find the measure of angle A to the nearest whole number.
Found 2 solutions by Alan3354, MathLover1:
Answer by Alan3354(69443) About Me  (Show Source):
You can put this solution on YOUR website!
Triangle ABC has side a = 11, b = 14
and c = 17.
Find the measure of angle A to the nearest whole number.
=============
Use the Cosine Law
---
a^2 = b^2 + c^2 - 2bc*cos(A)

Answer by MathLover1(20855) About Me  (Show Source):
You can put this solution on YOUR website!
Triangle ABC has side a+=+11,+b+=+14 and c+=+17.
use The Law of Cosines (also called the Cosine Rule)

a%5E2=c%5E2%2Bb%5E2+-2bc%2Acos%28A%29
2bc%2Acos%28A%29=c%5E2%2Bb%5E2-a%5E2
cos%28A%29=%28c%5E2%2Bb%5E2-a%5E2+%29%2F2bc
cos%28A%29=%2817%5E2%2B14%5E2-11%5E2+%29%2F%282%2A14%2A17%29
cos%28A%29=%28289%2B169-121+%29%2F476
cos%28A%29=%28337+%29%2F476
cos%28A%29=0.7079831932773109
A=cos%5E%28-1%29%280.7079831932773109%29
A=40.1192°
A=40°