ABCD patrat
AB=60cm
ΔBCE isoscel , E exterior ABCD.
EB= 50cm .
mas<BCE=180°-mas<DCB ⇒ mas<BCE=180°-90°
mas<BCE=90°
⇒Δ BCE dreptunghic isoscel.
⇒BC=CE=60cm. ⇒ CE= 60cm.
DE=DC+CE=60+60⇒DE=120cm.
avem ΔADE dreptunghic in D. ; Ad=l patrat = 60cm.
Arie Δ = AD · DE
2
AΔ= 60×120
2
AΔ = 3600cm²
se constata trapezul dreptunghic ABED cu AB||ED.
Arie ABED= (60+120) · 60
2
A ABED= 5400 cm²
Arie Δ ABE Arie trapez ABED - ArieΔADE
A Δ ABE = 5400-3600
A Δ ABE = 1 800 cm²
