If cos 2x = tan^2 y, show that cos 2y = tan^2 x How to do?
回答 (1)
2016-02-21 3:28 am
cos 2x = 2 cos² x - 1 = tan² y ----> 2 cos² x = tan² y + 1 = sec²y----> cos² y = 1 / [ 2 cos²x ] = sec² x / 2--->
2 cos² y = sec² x ----> cos 2y = 2 cos² y - 1 = sec² x - 1 = tan² x
2 cos² y = sec² x ----> cos 2y = 2 cos² y - 1 = sec² x - 1 = tan² x
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