SOLUTION: Hi, I am just beginning Precalculus, and am confused about the process that involves solving for theta where there are actually two answers. I kind of understand the concept (t

Question 650299: Hi,
I am just beginning Precalculus, and am confused about the process that involves solving for theta where there are actually two answers. I kind of understand the concept (the angle and its inverse, somehow) but do not know how to actually reach the two answers.
The problem I am looking at is cos (θ) = -√(3)/2
I have tried several methods that end in bizarre answers. Any help would be appreciated, thank you.
-Alex
Found 2 solutions by MathTherapy, solver91311:
Answer by MathTherapy(10555) (Show Source): You can put this solution on YOUR website!

Hi,
I am just beginning Precalculus, and am confused about the process that involves solving for theta where there are actually two answers. I kind of understand the concept (the angle and its inverse, somehow) but do not know how to actually reach the two answers.
The problem I am looking at is cos (θ) = -√(3)/2
I have tried several methods that end in bizarre answers. Any help would be appreciated, thank you.
-Alex

cos (θ) = ----- =

As the angle is cos and < 0, is in the 2nd quadrant, where its reference angle = , and in the 3rd quadrant where its reference angle =

OR

You could also look at the unit circle and see that:

= and in the 2nd and 3rd quadrants, respectively.

Send comments and �thank-yous� to �D� at MathMadEzy@aol.com
Answer by solver91311(24713) (Show Source): You can put this solution on YOUR website!

Here's a unit circle to supplement what MathTherapy said:

John

My calculator said it, I believe it, that settles it

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