Bài 29 (SBT trang 195)Tính các giá trị lượng giác của cung $\alpha$, biết : a) $\sin\alpha=0,6$ khi $0b) \(\cos\alpha=-0,7$ khi $\dfrac{\pi}{2}c) \(\tan\alpha=2$ khi $\pid) \(\cot\alpha=-3$ khi \(\dfrac{3\pi}{2}

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6 năm trước

Bài 29 (SBT trang 195)
Tính các giá trị lượng giác của cung $\alpha$ , biết :
a) $\sin\alpha=0,6$ khi $0< \alpha< \dfrac{\pi}{2}$
b) $\cos\alpha=-0,7$ khi $\dfrac{\pi}{2}< \alpha< \pi$
c) $\tan\alpha=2$ khi $\pi< \alpha< \dfrac{3\pi}{2}$

d) $\cot\alpha=-3$ khi $\dfrac{3\pi}{2}< \alpha< 2\pi$

Loga Toán lớp 10

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trancongpcccps4@gmail.com

Do $\dfrac{\pi}{2}< \alpha< \pi$ nên $sin\alpha>0;tan\alpha< 0;cot\alpha< 0$ .
$sin\alpha=\sqrt{1-cos^2\alpha}=\dfrac{\sqrt{51}}{10}$ .
$tan\alpha=\dfrac{sin\alpha}{cos\alpha}=\dfrac{\sqrt{51}}{10}:\left(-0,7\right)=-\dfrac{\sqrt{51}}{7}$ .
$cot\alpha=\dfrac{1}{tan\alpha}=\dfrac{-7}{\sqrt{51}}$ .

Vote (0) Phản hồi (0) 6 năm trước

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bai giai

Toán lớp 4

$\sqrt{2x-1}$ = $x$ + 1

Chứng minh bất đẳng thức:
$a^{^{ }2}+b^2+c^2+\dfrac{3}{4}\ge a+b+c$