Capital letter $H$ has $2$ lines of symmetry. 

In the figure, $A, B, C$ are points on a circle. $\angle \mathrm{ACB}=90°, \mathrm{AC}=12 \mathrm{cm}$ and $\mathrm{CB}=5 \mathrm{cm}$. Find the diameter of the circle.

$A, B, C$ and $D$ are points on a circle such that $ADC=90°, BAC=54°$ and $AD=CD$. Find $\angle \mathrm{DCA}$.

$A, B, C$ and $D$ are points on a circle such that $ADC=90°, BAC=54°$ and $AD=CD$. Find $\angle ABC$.

$A, B, C$ and $D$ are points on a circle such that $ADC=90°, BAC=54°$ and $AD=CD$. Find $\angle BCD.$