Trigonometry!!

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mathisntfun

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Mar 21, 2005
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There is a unit circle with an angle theta and an angle alpha but the angles are not given. There are 2 points on the circle. Theta has a point (-.985, -.174) and alpha has a point (.940, -.342) I need to find the sin of theta, cos of alpha. I also need to find theta and alpha itself.

Can someone please help me, I am confused on this one.
 
Theta has a point (-.985, -.174)

Draw a triangle from the origin (0,0) to this point back to the x axis (making a right angle) .
Now the triangle has a base of length = -0.985 and a height of -0.174

To find the hyp. use c^2 = (-0.985)^2 + (-0.174)^2

then you can use sin or cos to find the angle.

Repeat for the other point.

Have a go...
 
Ok I got c^2 = .970 + .030 which equals the square root of 1 correct? But how do you find theta? It also asks to find the sin of theta so would that be -.174 since that is the y coordinate?
 
Theta has a point (-.985, -.174)

sin theta = opposite/ hyp

sin theta = 0.174 /1

theta = 10.02 degrees
 
instead of theta = 10.02 degrees would theta = 190.02 degrees since it goes past the 180 line by adding 10.02 to 180 and then alpha instead of = 19.94 would you do 360 - 19.94 = 340.06?
 
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