Lượng giác

G

girltoanpro2

1. Ta có:
[TEX]sin2x+2tanx=3[/TEX]
[TEX]\frac{2tanx}{1+tan^2x}+2tanx=3[/tex]
[TEX]2tanx+2tanx(1+tan^2x)=3(1+tan^2x)[/TEX]
Rút gọn, giải phương trình bậc 3.
 
N

nguyenbahiep1

câu 2

$2.sinx.cosx ( \dfrac{cosx.cos2x + sin2x.sinx}{sinx.cos2x} )= 4.cos^2 x$
$\Leftrightarrow \dfrac{cos^2 x}{cos2x} = 2.cos^2 x$
$ \Rightarrow cos^2x = 0 (L) V cos2x = \frac{1}{2}$
 
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