1 reply to this topic

[Mi2]

C/m cos^4+sin^2cos^2+sin^2=1
Giúp mình gấp với.
Thanks mấy bạn nhiều

[tandatcr2000pro]

    $cos^4x+sin^2x.cos^2x+sin^2x$

$ = cos^4x+2sin^2x.cos^2x-sin^2x.cos^2x+sin^2x$

$ = cos^4x+2sin^2x.cos^2x+sin^2x(1-cos^2x)$

$ = cos^4x+2sin^2x.cos^2x+sin^4x$

$ = (cos^2x+sin^2x)^2$

$ = 1$