Find the measure of the largest angle in ABC if a = 12, b = 8 and c = 13.

78.28023969=C

Step-by-step explanation:

The largest angle is opposite the largest side so C would be the largest angle.

We can find C using the law of cosines

c^2 = a^2 + b^2 - 2ab cosC

13^2 = 12^2 + 8^2 - 2*12*8cosC

169 = 144 + 64 - 192 cos C

Combine like terms

169 = 208 - 192 os C

Subtract 208 from each side

-39 = - 192 cos C

Divide by - 192

-39/-192 = cos C

Take arccos of each side

acrcos (39/192) = arccos (cos C)

arccos (39/192) = C

78.28023969=C