Cho tan a= 2/5. Tính A= 3sin^2a + 5 sina.cosa – cos^2 / 2.cos^2 25/10/2021 Bởi Mary Cho tan a= 2/5. Tính A= 3sin^2a + 5 sina.cosa – cos^2 / 2.cos^2
$A=\frac{3sin^2a+5sina.cosa-cos^2a}{cos^2a}$ $= 3tan^2a+5tana-1$ $= 3.(\frac{2}{5})^2+5.\frac{2}{5}-1$ $= \frac{37}{25}$ Bình luận
$A=\frac{3sin^2a+5sina.cosa-cos^2a}{cos^2a}$
$= 3tan^2a+5tana-1$
$= 3.(\frac{2}{5})^2+5.\frac{2}{5}-1$
$= \frac{37}{25}$