math test help!!! sin/cos/tan?

J

John

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Which expression is equivalent to sin 150 degrees?

1) cos 30 degrees
2) sin 30 degrees
3) sin (-30 degrees)
4) - sin 30 degrees

Which expression is equivalent to cos 150 degrees?
1 ) cos 60 degrees
2) - cos degrees
3) cos 30 degrees
4) - cos 30 degrees
 
I think I just answered another one of your questions...

For number one, 150 degrees would have a reference angle of 30 and since it's in quadrant 2, sin would be positive, so the answer is Choice 2: Sin 30 degrees.

For number two, 150 degrees again has a reference angle of 30 degrees in quadrant 2. Cos is negative here, so the answer is choice 4: the negative cosine of 30 degrees.
 
sin(180-30) = sin30
the answer is 2 (as sin is positive in the 2nd quadrant_

cos(180-30) = -cos30
the answer is 4 (as cos is negative in the 2nd quadrant)
 
Which expression is equivalent to sin 150 degrees?
2) sin 30 degrees


Which expression is equivalent to cos 150 degrees?
4) - cos 30 degrees
 
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