Question #62ba8

1 Answer
Nghi N
Jan 22, 2018

#x = 20^@72 + k90^@#

Explanation:

#- 5sin 4x + 40cos 4x = 0#.
#sin 4x - 8cos 4x = 0#.
Divide both sides by cos 4x (condition #cos 4x != 0#)
tan 4x - 8 = 0
tan 4x = 8.
Calculator and unit circle give -->
#4x = 82^@87 + k360^@#
#x = 20^@72 + k90^@#

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