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by zack
Wed Feb 08, 2012 9:05 pm
Forum: Trigonometry
Topic: trig equation: find value of x in cos(3x)= -0.419 for 0<x<
Replies: 1
Views: 1859

trig equation: find value of x in cos(3x)= -0.419 for 0<x<

find the value of x cos(3x)= -0.419 for 0<x<270 I do arc cos -0.419 which equals 114.77 and then to find the second angle in the 3rd quadrant why do I need to minus 360 to get the degree in the 3rd quadrant? why not add 90 to 114.77 to make it in the 3rd quadrant? someone please explain this

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