1-cos^2x : 1-sin^2x + tanx.cotx = 1 : cos^2x help dùm e vs mọi người 04/09/2021 Bởi Autumn 1-cos^2x : 1-sin^2x + tanx.cotx = 1 : cos^2x help dùm e vs mọi người
$VT=\dfrac{1-\cos^2x}{1-\sin^2x}+\tan x\cot x\\ =\dfrac{\dfrac{1}{\cos^2x}-1}{\dfrac{1}{\cos^2x}-\dfrac{\sin^2x}{\cos^2x}}+1\\ =\dfrac{\tan^2x+1-1}{\tan^2x+1-\tan^2x}+1\\ =\tan^2x+1\\ =\dfrac{1}{\cos^2x}\\ =VP$ Bình luận
$VT=\dfrac{1-\cos^2x}{1-\sin^2x}+\tan x\cot x\\ =\dfrac{\dfrac{1}{\cos^2x}-1}{\dfrac{1}{\cos^2x}-\dfrac{\sin^2x}{\cos^2x}}+1\\ =\dfrac{\tan^2x+1-1}{\tan^2x+1-\tan^2x}+1\\ =\tan^2x+1\\ =\dfrac{1}{\cos^2x}\\ =VP$