\(\left(1+\tan^2\alpha\right)\cos^2\alpha+\left(1+\cot^2\alpha\right)\sin^2\alpha\)\(=\left(1+\frac{\sin^2\alpha}{\cos^2\alpha}\right)\cos^2\alpha+\left(1+\frac{\cos^2\alpha}{\sin^2\alpha}\right)\sin^2\alpha\)\(=\cos^2\alpha+\sin^2\alpha+\sin^2\alpha+\cos^2\alpha\)\(=2\sin^2\alpha+2\cos^2\alpha\)đúng hay sai zậy các...
Đọc tiếp
\(\left(1+\tan^2\alpha\right)\cos^2\alpha+\left(1+\cot^2\alpha\right)\sin^2\alpha\)
\(=\left(1+\frac{\sin^2\alpha}{\cos^2\alpha}\right)\cos^2\alpha+\left(1+\frac{\cos^2\alpha}{\sin^2\alpha}\right)\sin^2\alpha\)
\(=\cos^2\alpha+\sin^2\alpha+\sin^2\alpha+\cos^2\alpha\)
\(=2\sin^2\alpha+2\cos^2\alpha\)
đúng hay sai zậy các bạn
\(=2\) luôn, sao còn để dòng cuối làm gì?
nhìn vào là không thấy gì cả