Câu 15:
a: Sai
b: \(sin2x=-\dfrac{1}{2}\)
=>\(\left[{}\begin{matrix}2x=-\dfrac{\Omega}{6}+k2\Omega\\2x=\Omega+\dfrac{\Omega}{6}+k2\Omega=\dfrac{7}{6}\Omega+k2\Omega\end{matrix}\right.\)
=>\(\left[{}\begin{matrix}x=-\dfrac{\Omega}{12}+k\Omega\\x=\dfrac{7}{12}\Omega+k\Omega\end{matrix}\right.\)
\(x\in\left(0;\Omega\right)\)
=>\(\left[{}\begin{matrix}-\dfrac{\Omega}{12}+k\Omega\in\left(0;\Omega\right)\\\dfrac{7}{12}\Omega+k\Omega\in\left(0;\Omega\right)\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}k-\dfrac{1}{12}\in\left(0;1\right)\\k+\dfrac{7}{12}\in\left(0;1\right)\end{matrix}\right.\)
=>\(\left[{}\begin{matrix}k\in\left(\dfrac{1}{12};\dfrac{13}{12}\right)\\k\in\left(-\dfrac{7}{12};\dfrac{5}{12}\right)\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}k=1\\k=0\end{matrix}\right.\)
=>Có 2 nghiệm
=>Sai
c: Tổng các nghiệm trong khoảng từ 0 đến pi là:
\(-\dfrac{\Omega}{12}+1\cdot\Omega+\dfrac{7}{12}\Omega=\dfrac{6}{12}\Omega+\Omega=\dfrac{3}{2}\Omega\)
=>Đúng
d: Sai
Câu 13:
a: Đúng
b: Sai
c: Đúng
d: Sai
