Question #459f8

1 Answer
Nghi N.
Nov 5, 2015

simplify (sin x - cos x)(sin x + cos x)

Ans: -cos 2x

Explanation:

Apply the trig identity: #cos 2x = (cos^2 x - sin^2 x)#
#(sin x - cos x)(sin x + cos x) = sin^2 x - cos^2 x =#
# = - (cos^2 x - sin^2 x) = - cos 2x.#

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