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

$a=pi n,$  n Е Z

$a=2pi n -2tan^{-1}(1+-sqrt{2}+sqrt{2(2+-sqrt{2})}),$ n Е Z