SOLUTION: PLEASE HELP ME ! Find sin 2x, cos 2x, and tan 2x from the given information. tan x = − 15/8 , x in Quadrant II

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Question 1026523: PLEASE HELP ME !
Find sin 2x, cos 2x, and tan 2x from the given information.
tan x = − 15/8 , x in Quadrant II
Answer by rothauserc(4718) About Me  (Show Source):
You can put this solution on YOUR website!
tan^(-1) of -15/8 is approx -62 degrees
:
trig functions are periodic - we are looking for the angle in the second quadrant which is equivalent to -62 degrees, that angle is 180-62 = 118 degrees
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sin(118) = 0.88
cos(118) = -0.47
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sin 2x = 2sin(x)cos(x)
sin 2x = 2(0.88)(-0.47) = -0.83
:
cos 2x = 2cos^2(x) - 1
cos 2x = 2(-0.47)^2 - 1 = -0.56
:
tan 2x = (2tan(x)) / (1 - tan^2(x))
tan 2x = (2(-15/8)) / (1 - (-15/8)^2) = 1.49
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