SOLUTION: This problem refers to triangle ABC. If a = 40 cm, b = 12 cm, and c = 34 cm, find the largest angle. (Round your answer to the nearest whole number.) I've only got 33 so far

Algebra ->  Trigonometry-basics -> SOLUTION: This problem refers to triangle ABC. If a = 40 cm, b = 12 cm, and c = 34 cm, find the largest angle. (Round your answer to the nearest whole number.) I've only got 33 so far       Log On


   



Question 1169558: This problem refers to triangle ABC.
If a = 40 cm, b = 12 cm, and c = 34 cm, find the largest angle. (Round your answer to the nearest whole number.)
I've only got 33 so far which was incorrect.

Answer by ikleyn(52798) About Me  (Show Source):
You can put this solution on YOUR website!
.

The largest angle is opposite to the longest side.


By knowing is, we now can apply the cosine law to find cos(A), where A is the opposite angle to the side a= 40 cm


    a^2 = b^ + c^2 - 2bc*cos(A),


which implies


    cos(A) = %2812%5E2+%2B+34%5E2+-+40%5E2%29%2F%282%2A12%2A34%29 = -0.36765 = 1.9472 radians = 111.63 degrees.    ANSWER

Solved.