Thursday
May 5, 2016

# Homework Help: Trig

Posted by Jus on Sunday, May 31, 2009 at 12:05pm.

The angle 2x lies in the fourth quadrant such that cos2x=8/17.

1.Which quadrant contains angle x?
2. What is the measure of x, in radians?

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I know that angle 2x is in quadrant 4, but quadrant x...? I am not sure where it is and how to get the measure of it in radians.
• Trig - bobpursley, Sunday, May 31, 2009 at 12:10pm

Half of quadrant 4 is half of 270deg to 360 deg, or 135 to 190 deg, quadrant 2.

• Trig - Reiny, Sunday, May 31, 2009 at 12:57pm

switch your calculator to radians
enter
8
÷
17
=
to get .470588...
press 2ndF, then cos
to get 1.08084
This would be the radian measure in the first quadrant, but you are in the fourth,
so 2pi - 1.0804 = 5.20235
but this is 2x
so x = 5.20235/2
= 2.60117
(in degrees that would be 149.04º which is in compliance with what bobpursley told you above)

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