下列各组角中,可以作为向量的方向角的是(
)
A: $\frac{\pi }{3},\,\frac{\pi }{4},\,\frac{2\pi }{3}$
B: $-\frac{\pi }{3}\,,\frac{\pi }{4}\,,\frac{\pi }{3}$
C: $\frac{\pi }{6},\,\pi ,\,\frac{\pi }{6}$
D: $\frac{2\pi }{3},\,\frac{\pi }{3},\,\frac{\pi }{3}$
)
A: $\frac{\pi }{3},\,\frac{\pi }{4},\,\frac{2\pi }{3}$
B: $-\frac{\pi }{3}\,,\frac{\pi }{4}\,,\frac{\pi }{3}$
C: $\frac{\pi }{6},\,\pi ,\,\frac{\pi }{6}$
D: $\frac{2\pi }{3},\,\frac{\pi }{3},\,\frac{\pi }{3}$
举一反三
- $\arctan (-\sqrt{3})=$ A: $-\frac{\pi}{3}$ B: $\frac{\pi}{6}$ C: $\frac{\pi}{3}$ D: $-\frac{\pi}{6}$
- Solve $\int_{-\frac{1}{2}}^1{1-x^2}dx=$? A: $\frac{\pi}{3}+\frac{\sqrt{3}}{8}$. B: $\frac{\pi}{2}$. C: $\frac{\pi}{6}+\frac{\sqrt{3}}{4}$. D: $\frac{\pi}{4}$.
- 函数$f(x)=\sin x + \cos x,x \in [0,2 \pi]$的上凸区间为 A: $[0,\frac{\pi}{4}] \cup [\frac{5}{4} \pi,2 \pi] $ B: $[\frac{\pi}{4},\frac{5}{4} \pi]$ C: $[0,\frac{3}{4}\pi] \cup [\frac{7}{4} \pi,2 \pi] $ D: $[\frac{3}{4} \pi,\frac{7}{4} \pi] $
- 这时线圈平面法线方向与该处磁感强度的方向的夹<br/>角为____________________． A: `\frac{1}{3}\pi` B: `\frac{1}{6}\pi` C: `\frac{1}{2}\pi` D: `\frac{2}{3}\pi`
- 函数$f(x) =sin^3 x, x \in [0,2 \pi]$的单调递减区间为 A: $[\frac{\pi}{2},\frac{3}{2} \pi]$ B: $[\frac{3}{2} \pi,2 \pi]$ C: $[0,\frac{\pi}{2}]$ D: $[0,2 \pi]$