S四边形=S△ADC+S△ABC=1/2*2*5+1/2*3*5=5+7.5=12.5
C四边形=AD+DC+BC+AB=√5+2√5+√13+3√2=14.556≈14.56
∵AC^2=25 AD^2=5 DC^2=20
∴AC^2= AD^2+ DC^2
∴∠ADC=90°
S四边形=S△ADC+S△ABC=1/2*2*5+1/2*3*5=5+7.5=12.5
C四边形=AD+DC+BC+AB=√5+2√5+√13+3√2=14.556≈14.56
∵AC^2=25 AD^2=5 DC^2=20
∴AC^2= AD^2+ DC^2
∴∠ADC=90°