Question

Okay, so I'm looking for the cosine of a triangle with the following values. I have the answer of 0.4815, but the angle translates to 61.2. Can someone explain why this is so?

Values: a = 8 , b = 3 , c = 9.
The "proper" formula used to solve this is
cosA =b^2 + c^2 - a^2 / 2b(c) .

Answer 1

I understand how to solve for the answer, my issue is when to get from the decimal response to a legitimate angle.

Answer 2

That is, from 0.4815 to 61.2

Answer 3

I dont see how you got 61.2

Answer 4

This is a lesson that they've provided for me, and they're somehow telling me the decimal can change to that.

Answer 5

oh wait :) one moment

Answer 6

What about it?

Answer 7

the answer is 61.2 degrees, i get the same

Answer 8

1.068 radians

Answer 9

here is a law of cosines calculator
https://www.google.com/search?q=law+of+cosines+calculator&ie=utf-8&oe=utf-8

Answer 10

But I'd like to know how they were able to convert it, rather than just using a calculator.

Unless, that is what they did..

Answer 11

cos(A) = .4815

you have to take the inverse cosine to determine A

Answer 12

if your calculator is set to degrees, itll give you:

cos^(-1) (.4815) = 61.23

Answer 13

if its set to radians, then youll either have to set it to degrees, or adjust the results by 180/pi

Answer 14

It didn't give me the desired value.

Answer 15

what did it give you?

Answer 16

$$ \Large{
\cos A^o = 0.4185 \iff A^o = \cos^{-1}( 0.4185)
}
$$

Answer 17

Ah, never mind. I was in radian mode. Whoops. You're right, thank you.

Answer 18

yeah radians is 1.0684...

Answer 19

¯\_(ツ)_/¯

Answer 20

Alright, thanks for all the help.

Answer 21

good luck