SOLUTION: what is the value of the following function? cos(130�)cos(10�) + sin(10�) sin(130�).

Question 449095:
what is the value of the following function? cos(130�)cos(10�) + sin(10�) sin(130�).

Answer by lwsshak3(11628) (Show Source): You can put this solution on YOUR website!
what is the value of the following function? cos(130�)cos(10�) + sin(10�) sin(130�).
..
Addition formula for cosine:
cos(s-t)=cos s cos t+sin s sin t
For given equation:
cos(130�)cos(10�) + sin(130�) sin(10�)=cos(130�-10�)=cos 120�
In standard position 120� terminates in quadrant II where cos is negative.
reference angle=180-120 =60�
cos 60�=-1/2
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