Question

Use the Law of Cosines to find the measure of angle S to the nearest degree. (Enter only the number.)

I don't know if I'm doing something in the process wrong, but the answer I'm getting is too high. I'll attach the photo.

Answer 1

I know the formula is a^2=b^2+c^2-2bc cosA but I'm doing something wrong somewhere.

Answer 2

which angle do you want?

Answer 3

Angle S

Answer 4

ooh S
ok
you want the angle not the side, so start by solving \[ a^2=b^2+c^2-2bc\cos(A)\] for \(\cos(A)\)

Answer 5

you get
\[\cos(A)=\frac{b^2+c^2-a^2}{2bc}\]

Answer 6

then since you want the angle, not the cosine of the angle, take the arccosine of whatever number you get

Answer 7

you good from there?

Answer 8

Thank you so much! The lesson never really went over HOW to solve so I never knew where to divide and all that. Now I understand. And I got S=39.7

Answer 9

i didn't do it, but i believe you
it is a calculator exercise now
yw
btw \(\cos(A)=\frac{b^2+c^2-a^2}{2bc}\) is not hard to memorize, you don't really want to solve each time

Answer 10

Okay awesome! Again thanks so much!