Question 315698
sin{2theta}=-cos{{7pi}/4} for 0 to 2pi
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7pi/4 = 315º

cos(7pi/4) = sqrt(2)/2

sin(2T) = -sqrt(2)/2

2T = 225,  315, 585, 675

2T = 5pi/4, 7pi/4, 13pi/4, 15pi/4

theta = 5pi/8, 7pi/8, 13pi/8, 15pi/8