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Mathematics
Mathematics
Problem
Which of the following is NOT an equivalent expression for
cos
2
θ
\cos 2\theta
cos
2
θ
? a)
cos
4
θ
−
sin
4
θ
\cos^{4}\theta-\sin^{4}\theta
cos
4
θ
−
sin
4
θ
b)
1
−
2
cos
2
θ
1-2\cos^{2}\theta
1
−
2
cos
2
θ
c)
1
−
tan
2
θ
1
+
tan
2
θ
\displaystyle\frac{1-\tan^{2}\theta}{1+\tan^{2}\theta}
1
+
tan
2
θ
1
−
tan
2
θ
d)
cos
2
θ
−
sin
2
θ
\cos^{2}\theta-\sin^{2}\theta
cos
2
θ
−
sin
2
θ
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