Cho cos a = -12/13 và pi/2 Question Cho cos a = -12/13 và pi/2 in progress 0 Toán Alexandra 1 năm 2021-07-28T16:11:13+00:00 2021-07-28T16:11:13+00:00 1 Answers 9 views 0 Answers ( ) dananh 0 2021-07-28T16:12:43+00:00 28/07/2021 at 16:12 Reply Đáp án: $\sin a=\dfrac{5}{13}\\ \tan a=\dfrac{-5}{12}$ Giải thích các bước giải: $\sin^2a+\cos^2a=1\\\Rightarrow \sin^2a=1-\cos^2a=1-\left ( \dfrac{-12}{13} \right )^2=\dfrac{25}{169}\\\Rightarrow \sin a=\pm \dfrac{5}{13}$Vì $\dfrac{\pi}{2}<a<\pi$Nên $\sin a>0\Rightarrow \sin a=\dfrac{5}{13}$$\Rightarrow \tan a=\dfrac{\sin a}{\cos a}=\dfrac{\dfrac{5}{13}}{\dfrac{-12}{13}}=\dfrac{-5}{12}$ Leave an answer Name* E-Mail* Website Featured image Select file Browse Captcha* 35:5x4+1-9:3 = ? ( ) Answer* Click here to cancel reply. Alexandra About Alexandra
Answers ( )
Đáp án:
$\sin a=\dfrac{5}{13}\\
\tan a=\dfrac{-5}{12}$
Giải thích các bước giải:
$\sin^2a+\cos^2a=1\\
\Rightarrow \sin^2a=1-\cos^2a=1-\left ( \dfrac{-12}{13} \right )^2=\dfrac{25}{169}\\
\Rightarrow \sin a=\pm \dfrac{5}{13}$
Vì $\dfrac{\pi}{2}<a<\pi$
Nên $\sin a>0\Rightarrow \sin a=\dfrac{5}{13}$
$\Rightarrow \tan a=\dfrac{\sin a}{\cos a}=\dfrac{\dfrac{5}{13}}{\dfrac{-12}{13}}=\dfrac{-5}{12}$