Răspuns:
Explicație pas cu pas:
I
1) A=l×h/2=20×1,7/2=1,7×10=17 cm²
2)A=70 cm² l=10cm ⇒h=2A/l=2×70/10=14 cm
3)A=BC×h1/2=12×5/2=6×5=30cm²
A=AC×h2/2 ⇒h2=2A/AC=2×30/4=30/2=15 cm
4)A Δdreptunghic=c1×c2/2=12×15/2=6×15=90 cm²
5)c2=2AΔdr/c1=2×350/7=2×50=100 cm
II
1)A=l²=1,2²=1,44 cm²
2)P=104 cm=4l ⇒l=P/4=104/4=26 cm
3)A=l²=81 cm² ⇒l=√A=9 cm ⇒P=4l=4×9=36 cm
4)Acod=Aabcd:4
Aabcd=l²=64 cm² ⇒Acod=64:4=16 cm²
III
1)A=L×l=9×18=162 cm²
P=2(L+l)=2(18+9)=2×27=54cm
2)P=2(L+l)=40 ⇒L+l=20
L=l+2 ⇒l+2+l=20 ⇒2l=18 ⇒l=9cm
IV
1)A=2×(BC×d(A, BC))/2=BC×d(A, BC)=18×13=234 cm²
2)A=l×h =36 cm² ⇒h=A/l=36/9=4 cm
V
1)A=d1×d2/2=6×14/2=6×7=42 cm²
2)A=48cm² d1=6 cm ⇒d2=2A/d1=2×48/6=2×8=16 cm
3)A=2AB×dist (C, AB)/2= AB×dist (C, AB)
AB= A/AB×dist (C, AB)=40/4=10 cm
4)∡BAD=60° ⇒ ΔBAD echlateral ⇒BD=AB=AD AB=12 cm
VI
1)Lmijl=(B+b)/2=18 cm si h=7 cm ⇒A=Lmijl×h
A=18×7=126 cm²
2)Atrp=82 cm²=(B+b)×h/2 h=2A/(B+b)=2×820/(21+20)=2×2×41×10/41=40cm
3)Afghi=Aegh-Aefi=87 cm²-25 cm²=62 cm²
Aegm=Aegh/2=87cm²/2=43,5 cm²
