Toán 11: Chứng minh: (sinx+cosx)^2=1+2sinxcosx, sin^4⁡x+cos^4⁡x=1-2 sin^2⁡x cos^2⁡x

(sinx+cosx)^2=1+2sinxcosx
sin^4⁡x+cos^4⁡x=1-2 sin^2⁡x cos^2⁡x
tan^2⁡x-sin^2⁡x=tan^2⁡x sin^2⁡x
sinxcosx(1+tanx)(1+cotx)=1+2sinxcosx

#ToanLop11
#LuongGiac
#Trigonometry