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Richard Kozik






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This message was updated on 2/26/2008 5:03:33 AM by Richard Kozik



Trig identities
posted on: 2/26/2008 5:00:14 AM

Howdy all! First I want to say thank goodness there are folks like you helpful ones who assists us, the mentally challenged, with our problems with Trig. Here is my problemo:

Find the exact values of sin2 a (those're alpha characters), cos2 a and tan2 a; given this information: cos a = -(4/5)

90degrees < a < 180degrees.

To be honest I am lost and shant know where to begin. I know I need to apply half-angle identities, right? I was told this falls into quadrant IV, but I don't know how the 90 to 180 deg information tells us that.
Man I sure appreciate the help more than you know. Thnkx rich

 



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