增大字号
减小字号
数学课前练习
1. 已知\(\sin\alpha+\cos\alpha=\displaystyle \frac{1}{5}(0<\alpha<\pi)\),则\(\tan2\alpha=\)()
A. \(-\dfrac{24}{7}\)
B. \(\dfrac{24}{7}\)
C. \(-\dfrac{24}{25}\)
D. \(\dfrac{24}{25}\)
提交答案
2. 已知\(\cos(\alpha-\beta)=\displaystyle \frac{7}{12}\),\(\sin\alpha\sin\beta=\displaystyle \frac{1}{3}\),则\(\sin2\alpha\sin2\beta=\)()
A. \(\dfrac{1}{2}\)
B. \(\dfrac{1}{3}\)
C. \(\dfrac{1}{4}\)
D. \(\dfrac{1}{6}\)
提交答案