Question

Will fan if solved!!!
Find theta to 4 significant digits for 0 12 years ago

Answer 1

@Hero @nincompoop

Answer 2

Note that \[ cos(\theta ) = -.8759\]
Is asking what angle will give you an x-coordinate of -.8759, so you have to use inverse trig function arccos (sometimes noted as cos^-1)

Take the arccos of each side:

\[ arccos(cos(\theta)) = arccos(-.8759) \]

Since arccos is the inverse of cos, it will undo what cos has done so we get:

\[ \theta = arccos(-.8795) = cos^{-1}(-.8795)\]

Gotta be careful, since you have TWO potential angles that could result in your x coordinate of -.8795, see picture attached)

Theta_1 is what the calculator will return, but from the image, you can see we can derive the second solution from the equation

\[ \theta_2 = 2 \pi - \theta_1 \]

I ran the numbers and obtained one of your solutions, so it should work. I hope I made it clear enough.

Answer 3

ahhh thanks

Answer 4

use arccos right?