Semi-Circle and Semi-Circular Region

AB is the diameter of the circle whose length is $5 cm$, if $BC=4 cm$, find the length of $AC$.

In the given figure, $O$ is the centre of a circle and $\angle BDC=32°$. Find the $\angle ACB$.

In the given figure, $AB$ is a diameter of the circle such that $\angle PAB=45°$. Find $\angle PCA$.

In the given figure, $O$ is the centre of the circle. Find the value of $x$.