Posted by Anonymous on Monday, March 22, 2010 at 2:14pm.
Suppose sin theda= – 3/5 and theda is a Quadrant III angle.
Find the exact value of sin 2 theda and cos 2 theda.

trig  tradejack, Monday, March 22, 2010 at 2:39pm
It is theta not theda. Quadrant III= a reflex angle greater than 180 degrees and yet less than or = to 270 degrees.

trig  tradejack, Monday, March 22, 2010 at 2:39pm
as measured counterclockwise from the origin (0,0).

trig  Reiny, Monday, March 22, 2010 at 3:46pm
since sinØ = 3/5, in the third quad cosØ = 4/5
sin 2Ø = 2sinØcosØ = 2(3/5)(4/5) = 24/25
cos 2Ø = cos^2 Ø  sin^2 Ø = 16/25  9/25 = 7/25