A triangle has sides A, B, and C. Sides A and B are of lengths 4 and 9, respectively, and the angle between A and B is (5pi)/12 . What is the length of side C?

1 Answer
Aug 10, 2016

C=8.85

Explanation:

As per law of cosines
C^2=A^2+B^2-2Atimes Btimescos(theta) where A=4;B=9 and theta=(5pi)/12
or
C^2=4^2+9^2-2times4times9timescos((5pi)/12)
or
C^2=16+81-72times(0.2588)
or
C^2=16+81-18.63
or
C^2=78.37
or
C=sqrt78.37
or
C=8.85