Question

Use the law of cosines to find the value of 2, 3, 4 cos (theta).

Answer 1

What are those dots in between the 2 and the 3 and the 4?

Answer 2

I think those are multiplication signs.

Answer 3

I think the point of it is that they want you to find the angle, theta, by means of the Law of Cosines. Then, confirm you actually did by evaluating the expression, 2*3*4*cos(theta)

Answer 4

so multiply 2*3*4*cos(theta)?

Answer 5

That doesn't sound right. You can just work backwards.

Answer 6

Sorry, I'm not too sure lol.

Answer 7

\[\cos(\theta)=\frac{3^2+4^2-2^2}{2\times 3\times 4}\]

Answer 8

once you compute that number, take the arccosine of it to find \(\theta\)

Answer 9

ooh doh nvm it is not asking for \(\theta\) it is asking for
\[2\times 3\times 4\cos(\theta)\] that is just
\[3^2+4^2-2^2\]

Answer 10

the dots are times signs

Answer 11

@satellite73 3^2+4^2−2^2=21

Answer 12

I'm still a little confused as to how to set this up for future questions

Answer 13

it is a goofy question is why

Answer 14

^

Answer 15

so I guess the answer would be a. 21 then?

Answer 16

in general
\[a^2=b^2+c^2-2ab\cos(A)\] is the law of cosines
if you solve for \(\cos(\theta)\) you get \[\cos(A)=\frac{b^2+c^2-a^2}{2bc}\]

Answer 17

no i screwed that up

Answer 18

\[a^2=b^2+c^2-2bc\cos(A)\]

Answer 19

second part is right

Answer 20

@satellite73 but the answer is a. 21 right?