tga+ctga=6则sin2a=
问题描述：
tga+ctga=6则sin2a=
答
tga+ctga=6
而tga+ctga=sina/cosa+cosa/sina=[（sina）^2+(cosa)^2]/(sinacosa)
=1/(sinacosa)
依题意：1/(sinacosa)=6
故sinacosa=1/6
sin2a=2*sinacosa=2*1/6=1/3
答
tga+ctga
=sina/cosa+cosa/sina
=1/(sinacosa)
=2/sin2a=6
所以sin2a=1/3
答
tga+ctga=6
tga+1/tga=6
((tga)^2+1)/tga=6
(tga)^2+1=6tga
sin2a
=2tga/(1+tg^2 a)
=2tga/6tga
=1/3