7 0*(ctg2x)³- 7* 3*(ctg2x)²*(-1/sin²2x)*2 -42 *-((соs²2x+sin²2x)/sin)
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(ctg2x)³ (ctg 2x)⁶ (ctg2x)⁴
-42 *-((соs²2x+sin²2x)/sin) 42*(сtg²2x+1) 42ctg²2x + 42
= ----------------------------------------- = ---------------------- = --------------------
(ctg2x)⁴ (ctg2x)⁴ (ctg2x)⁴