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Mathematics
Mathematics
Problem
Show that
cos
2
θ
=
1
−
tan
2
θ
1
+
tan
2
θ
\displaystyle \cos 2\theta = \dfrac{1-\tan^2\theta}{1+\tan^2\theta}
cos
2
θ
=
1
+
tan
2
θ
1
−
tan
2
θ
.
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