\sin^2x=1-\cos^2x;\\
\sin2=\pm\sqrt{1-\cos^2x}=\pm\sqrt{1-\left(\frac12\right)^2}=\pm\sqrt{1-\frac14}=\\
=\pm\sqrt{\frac44-\frac14}=\pm\sqrt{\frac{4-1}{4}}=\pm\sqrt{\frac34}=\pm\frac{\sqrt{3}}{2};\\
\sin2x=2\cdot\left(\pm\frac{\sqrt3}{2}\right)\cdot\frac12=\pm\frac{\sqrt3}{2}." alt="\cos x=\frac12;\\
\sin2x-?;\\
\sin2x=2\cdot\sin x\cdot\cos x;\\
\sin^2x+\cos^2x=1;==>\sin^2x=1-\cos^2x;\\
\sin2=\pm\sqrt{1-\cos^2x}=\pm\sqrt{1-\left(\frac12\right)^2}=\pm\sqrt{1-\frac14}=\\
=\pm\sqrt{\frac44-\frac14}=\pm\sqrt{\frac{4-1}{4}}=\pm\sqrt{\frac34}=\pm\frac{\sqrt{3}}{2};\\
\sin2x=2\cdot\left(\pm\frac{\sqrt3}{2}\right)\cdot\frac12=\pm\frac{\sqrt3}{2}." align="absmiddle" class="latex-formula">