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

State the exact values of the following.

cos(360 degrees)
sec(7pi/2)
tan(-9pi/2)

How do I do these?
Thanks!

  • Math - , Friday, December 9, 2011 at 3:04pm

    Remember 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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