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October 20, 2014

October 20, 2014

Posted by **Jillian** on Friday, December 9, 2011 at 2:05pm.

cos(360 degrees)

sec(7pi/2)

tan(-9pi/2)

How do I do these?

Thanks!

- Math -
**Steve**, Friday, December 9, 2011 at 3:04pmRemember you can add or subtract 2pi = 360° without changing the values of the trig functions.

Then recall that for sin,tan,ctn,csc, f(-x) = -f(x)

for cos, sec, f(-x) = f(x)

cos 360° = cos(360°-360°) = cos 0°

sec(7pi/2) = sec(7pi/2 - 4pi) = sec(-pi/2) = sec(pi/2)

tan(-9pi/2) = tan(-9pi/2 + 4pi) = tan(-pi/2) = -tan(pi/2)

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