Question

Find the perimeter of cyclic quadrilateral $PQRS$ if $PQ=20$ cm, $QR=15$ cm and $RS=7$ cm.

Answer 1

$P{Q}^2+Q{R}^2=P{R}^2\Rightarrow (20{)}^2+(15{)}^2=400+225$$=(25{)}^2$

$R{S}^2+P{S}^2=P{R}^2\Rightarrow 49+P{S}^2=P{R}^2=625$

$P{S}^2=576=(26{)}^2$

$\Rightarrow PS=26$

Perimeter $=20+15+7+26=68$