Rút gọn $\frac{sin2a – 2sin^2a}{sin2a – 2cos^2a}$= – tana 27/10/2021 Bởi Amaya Rút gọn $\frac{sin2a – 2sin^2a}{sin2a – 2cos^2a}$= – tana
$\dfrac{\sin2a-2\sin^2a}{\sin2a-2\cos^2a}$ $=\dfrac{2\sin a\cos a-2\sin^2a}{2\sin a\cos a-2\cos^2a}$ $=\dfrac{2\sin a(\cos a-\sin a)}{2\cos a(\sin a-\cos a)}$ $=\dfrac{-\sin a}{\cos a}$ $=-\tan a$ Bình luận
Đáp án: VT= $\frac{sin2a-2sin^{2}a}{sin2a-2cos^{2}a}$ = $\frac{2sinacosa-2(1-cos^{2}a)}{2sinacosa-2(1-sin^{2}a)}$ = $\frac{2(sinacosa- 1+cos^{2}a)}{2(sinacosa-1+sin^{2}a)}$ = $\frac{sinacosa- sin^{2}a}{sinacosa-cos^{2}a}$ = $\frac{-sina( sina-cosa)}{cos( sina-cosa)}$ = $\frac{-sina}{cosa}$ = -tana = VP Bình luận
$\dfrac{\sin2a-2\sin^2a}{\sin2a-2\cos^2a}$
$=\dfrac{2\sin a\cos a-2\sin^2a}{2\sin a\cos a-2\cos^2a}$
$=\dfrac{2\sin a(\cos a-\sin a)}{2\cos a(\sin a-\cos a)}$
$=\dfrac{-\sin a}{\cos a}$
$=-\tan a$
Đáp án:
VT= $\frac{sin2a-2sin^{2}a}{sin2a-2cos^{2}a}$
= $\frac{2sinacosa-2(1-cos^{2}a)}{2sinacosa-2(1-sin^{2}a)}$
= $\frac{2(sinacosa- 1+cos^{2}a)}{2(sinacosa-1+sin^{2}a)}$
= $\frac{sinacosa- sin^{2}a}{sinacosa-cos^{2}a}$
= $\frac{-sina( sina-cosa)}{cos( sina-cosa)}$ = $\frac{-sina}{cosa}$
= -tana = VP