phuong trinh luong giac

N

nguyenbahiep1

giai phuong trinh:
[TEX]3(1+\frac{\cos2x}{\cos^2x})^4+\tan^6x=4.[/TEX]

[laTEX]3( 1+ \frac{1}{cos^2x} - 2tan^2x)^4 + tan^6x = 4 \\ \\ 3(2-tan^2x)^4 + tan^6x = 4 \\ \\ tan^2x = u \geq 0 \\ \\ 3(2-u)^4 + u^3 -4 = 0 \\ \\ (u-1)(3u^3-20u^2+52u-44) = 0 [/laTEX]
 
Top Bottom