The lengths of the sides of triangles are $a=15 \mathrm{cm}$, $b=20 \mathrm{cm}$ and $c=25 \mathrm{cm}$. Check whether it is right-angle triangle?

In a $∆ABC$, $\angle B=35°$ and  $\angle C=55°$. Check whether the following is true: 

$A{C}^2=A{B}^2+B{C}^2$

In a $∆ABC$, $\angle B=35°$ and  $\angle C=55°$. Check whether the following is true: 

$A{B}^2=B{C}^2+A{C}^2$

In a $∆ABC$, $\angle B=35°$ and  $\angle C=55°$. Check whether the following is true: 

$B{C}^2=A{B}^2+A{C}^2$

A $15m$-long ladder is placed against a wall to reach a window $12 m$ high. Find the distance of the foot of the ladder from the wall.

A $5 \mathrm{m}$ long ladder when set against the wall of a house reaches a height of $4.8 \mathrm{m}$. How far is the foot of the ladder from the wall?