sin^2 (x) + cos^2 (x) = 1
cos (x) = - √ (1-sin^2 (x) = √ (1-4/25) = - √ (21/25) = - √21 / 5
sin2x - синус двойного угла
sin2x = 2sinxcosx = 2 * (-2/5) * (-√21 / 5) = 4√21 / 25
sin2x+6,6=4√21 / 25 + 66/10 = 16√21 / 100 + 660/100 = (660+16√21) / 100
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