1)
∠B=∠D
∠A=∠C
∠A+40*=∠D
∠C+40*=∠B
∠A+∠B+∠C+∠D=360*=2∠B+2∠C
2(∠C+40*)+2∠C=360*
2∠C+80*+2∠C=360*
4∠C=280*
∠C=70*
∠D=(360*-2∠C) : 2 = (360* - 140*) : 2 = 110*
Ответ: ∠C=70*, ∠D=110*.
2)
AB*2=BC
AB+BC+CD+DA=2AB+2BC=120см
2AB+2(2AB)=120см
6AB=120см
AB=20см=CD
AD=(120см-AB-CD) : 2 = (120см-20см-20см) : 2 = 40см
Ответ: AD=40см, CD=20см.