докажите тождество:cos2a-tga*ctga/sin2a-1=1/ctg2a

Question

докажите тождество:cos2a-tga*ctga/sin2a-1=1/ctg2a

Answer 1

cos2a-tga*ctga/sin2a-1=1/ctg2a

cos(2a)/ sin(2a)-1 - 1/ sin(2a)-1 = tan(2a)

2sin^2(a)/(cos(a)-sin(a))^2 = tan(2a)

sin(a) (tan92a)-1)=0

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