SOLUTION: Find the exact values using double angle formulas: a) cos 112.5 degrees b) tan 22.5 degrees

Question 544713: Find the exact values using double angle formulas:
a) cos 112.5 degrees
b) tan 22.5 degrees
Answer by lwsshak3(11628) (Show Source): You can put this solution on YOUR website!
Find the exact values using double angle formulas:
a) cos 112.5 degrees
b) tan 22.5 degrees
**
I think you meant using half-angle formulas:
..
a) cos 112.5�= cos (225/2)�=-√[(1+cos 225�)/2)]
1+cos 225�=1-√2/2=(2-√2)/2
(1+cos 225�)/2)=(2-√2)/4
-√[(1+cos 225�)/2)]=-√(2-√2)/2
cos 112.5�=-√(2-√2)/2
..
b) tan22.5�=tan (45/2)�=(sin 45�)/(1+cos 45�)=√2/2/(1+√2/2)
tan 22.5�=√2/(2+√2)
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