# Thread: Law of Cosines - Solve This Triangle

1. ## [SOLVED]Law of Cosines - Solve This Triangle

Law of cosines problem:

"Use the Law of Cosines to solve the triangle."
...............C
............./..|
.........../....|
5.4 yd /......|4.2 yd
......../.......|
......./.......|
.....A------B
......2.1 yd

So,
M<A=
M<B=
M<C=
a=4.2 yd
b=5.4 yd
c=2.1 yd

I never wind up with the correct angle degrees. In the back of my book, it seems like the answers are always off of what I have calculated. Does anyone know how this might have happened?

For M<A, I got 45.41 degrees. Hopefully that is the right answer.

Thanks for any help in advance.
-Alex

2. ## Re: Law of Cosines - Solve This Triangle

I made calculations for angle A by using the cosine formula that is Cos A = (b^2+c^2-a^2)/2bc and the value I got is 45.38 degrees. Little variation in such questions should be acceptable for approximations / rounding off.

3. ## Re: Law of Cosines - Solve This Triangle

Originally Posted by ibdutt
I made calculations for angle A by using the cosine formula that is Cos A = (b^2+c^2-a^2)/2bc and the value I got is 45.38 degrees. Little variation in such questions should be acceptable for approximations / rounding off.
thanks.