Bonjour
• Si ABC est isocèle en A :
[ABC isocèle en A <=> AB = AC]
AB + BC + AC = 10 cm
AB + BC + AB = 10 cm
2 × AB + BC = 10 cm
BC = 10 cm - 2 × AB
BC = 10 cm - 2 × 4 cm = 10 cm - 8 cm = 2 cm
AC = AB = 4 cm
SOLUTION:
BC = 2 cm
AC = 4 cm
• Si ABC est isocèle en B :
[ABC isocèle en B <=> AB = BC]
AB + BC + AC = 10 cm
AB + AB + AC = 10 cm
2 × AB + AC = 10 cm
AC = 10 cm - 2 × AB
AC = 10 cm - 2 × 4 cm = 10 cm - 8 cm = 2 cm
BC = AB = 4 cm
SOLUTION:
AC = 2 cm
BC = 4 cm
• Si ABC est isocèle en C :
[ABC isocèle en C <=> AC = BC]
AB + BC + AC = 10 cm
AB + BC + BC = 10 cm
AB + 2 × BC = 10 cm
2 × BC = 10 cm - AB
BC = (10 cm - AB) ÷ 2
BC = (10 cm - 4 cm) ÷ 2 = 6 cm ÷ 2 = 3 cm
AC = BC = 3 cm
SOLUTION:
AC = 3 cm
BC = 3 cm
