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Mathematics
Mathematics
Problem
Which one of the following equals
cos
2
θ
\cos 2\theta
cos
2
θ
for all real
θ
\theta
θ
? a)
2
sin
θ
cos
θ
2\sin\theta\cos\theta
2
sin
θ
cos
θ
b)
1
−
2
cos
2
θ
1-2\cos^2\theta
1
−
2
cos
2
θ
c)
cos
2
θ
−
sin
2
θ
\cos^2\theta-\sin^2\theta
cos
2
θ
−
sin
2
θ
d)
sin
2
θ
−
cos
2
θ
\sin^2\theta-\cos^2\theta
sin
2
θ
−
cos
2
θ
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