Question

A triangle has sides A, B, and C. Sides A and B are of lengths `7` and `12`, respectively, and the angle between A and B is `(7pi)/12`. What is the length of side C?

Answer 1

`C=15.4`

Explanation:

As per law of cosines
`C^2=A^2+B^2-2Atimes Btimescos(theta)` where `A=7;B=12 and theta=(7pi)/12`
or
`C^2=7^2+12^2-2times7times12timescos((7pi)/12)`
or
`C^2=49+144-168times(-0.2588)`
or
`C^2=49+144+43.48`
or
`C^2=236.4.8`
or
`C=sqrt236.48`
or
`C=15.4`