(adsbygoogle = window.adsbygoogle || []).push({}); 1. The problem statement, all variables and given/known data

In triangle ABC where you only know the sides: a, b and c I must find angle B.

a=8

b=6

c=12

2. Relevant equations

Law of cosines: c^2 = a^2 + b^2 -2ab*cos(C)

When angle C is at the opposite of side c, (same for a and b)

3. The attempt at a solution

12^2 = 6^2 + 8^2 -2*6*8*cos(C)

144 = 36+64-96cos(C)

44=-96cos(C)

-(44/96) = cos(C)

- (11/24) = cos(C)

(I know the answer is supposed to be 117.4)

And cos(117.4)=-(11/24)

The problem is:

How do I find the angle? The explanation says: "Use calculator (degree mode)"

How do I do that?

I have an TI-84 Plus

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# Homework Help: Law of cosine

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