Write down by looking at the adjoining picture:

Name of a semicircle.

What is the circumference of the largest circle which can be inscribed in a square of side $14 cm$? ($\mathrm{\pi }=\frac{22}{7}$)

In the given figure, $ABCDE$ is a pentagon inscribed in a circle such that $AC$ is a diameter and side $BC\parallel AE$. If $\angle BAC=50°$, find giving reason $\angle ACB$.