Trig help

[lilmacstew]

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I knwo that this may seem stupid, but I am soooo frazeled at this point that I am just lost, and ready for this semester to be over. Plus I HATE HATE HATE trig. Anthing to do with triangles lol
anyways here is the problem. Please help out, and don't make fun of me!!!! 😕

Solve, find exact solutions cos2and0with line through it + cos0withline through it = 0degrees for 0degrees<= 0withline through it < 360 degrees

 

[acretinmelon]

Is it the cosine squared of theta or the cosine of 2theta?

 

[lilmacstew]

it is 2theta

 

[ManchotPi]

--

 

[No Egrets]

Originally posted by lilmacstew
I knwo that this may seem stupid, but I am soooo frazeled at this point that I am just lost, and ready for this semester to be over. Plus I HATE HATE HATE trig. Anthing to do with triangles lol
anyways here is the problem. Please help out, and don't make fun of me!!!! 😕

Solve, find exact solutions cos2and0with line through it + cos0withline through it = 0degrees for 0degrees<= 0withline through it < 360 degrees

cos(2 theta) + cos(theta) = 0

one answer is 60 degrees. there might be more (?) but it's been about seven years since i took trig.

 

[Optimist]

Originally posted by No Egrets
cos(2 theta) + cos(theta) = 0

one answer is 60 degrees. there might be more (?) but it's been about seven years since i took trig.

I think 180 might be another.

 

[cwb]

You should buy a ti-89 or 92, it'll save you a lot of time and headaches.

 

[blaceel]

Yes, follow ManchotPi's suggestion and you will end up with the equation cos(theta) = 0.5 or -1. This leads to the three solutons 60, 180, and 300 degrees, or in radians, pi/3, pi, and 5pi/3.