so there's a triangle,

A= 45 degrees
B= ?
C= ?

b=5
a=?
c= 3√2

So for this triangle, since it's side angle side, I decided to use the law of cosines, and since we need to find side a, I used the formula,

a^2=b^2+c^2-2bcCos(A)

So I did √(5^2+3√(2)^2-2(5)(3√(2))Cos(45 degrees)

But I'm not getting the answer, which is √13

What am I doing wrong?

I can't understand the symbols... can you type them manually instead of copy/pasting?

EDIT: Thinking about it for a while, did you mean 3'2 ?

Use consistent units if that's the case.

I think I have it figured out - the strange symbol you're trying to copy and paste is the square root. In the future please write out the equations, or you can use shorthand like "sqrt" to make it clear.

You have the right formula, so it must be a simple math error you're making:


\angle A = 45^{\small o} \\
b = 5\\
c = 3\sqrt{2}


and so


a^2 = b^2 + c^2 - 2bc \cos(A) \\
a^2 = 5^2 + (3 \sqrt 2 )^2 -2(5)(3 \sqrt 2)\frac {\sqrt 2} 2 = 25 + 18 -30 =13\\
a = \sqrt {13}