(1+tanα)/(1-tanα)=(cosα+sinα)/(cosα-sinα)=2+√3
(cosα+sinα)^2/cos(2α)=(cosα+sinα)/(cosα-sinα)=2+√3
(1+sin(2α))/(1-sin(2α))=(2+√3)^2=7+4√3、sin(2α)=tとおくと、
(7+4√3)(1-t)=1+t、t=-(3+2√3)(√3-2)/2=√3/2、cos^2(2α)=1-sin^2(2α)=1/4、cos(2α)=±1/2
sin^2(α)=(1-cos(2α))/2、cos^2(α)=(1+cos(2α))/2、sin^2(α)=1/4, 3/4、cos^2(α)=3/4, 1/4、
sin(α)=±1/2, ±√3/2、cos(α)=±√3/2, ±1/2 、(sin(α),cos(α))=(±1/2,±√3/2)