Question #f4ec8

1 Answer
Nghi N.
Jul 22, 2015

sin 4x = cos 5x, is it true?
Ans: Not true

Explanation:

#sin 4x = cos 5x = sin (pi/2 - 5x)#
Take an example. #x = pi/4#

#sin (4x) = sin pi = 0#

#sin (pi/2 - 5x) = sin (pi/2 - 5pi/4) = sin (-3pi/4)

Therefor, the identity is not true.

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