7. Perhatikan gambar berikut.

Jawaban:

a). keliling ∆segitiga ABC

AD + DB = 10 cm + 10 cm = 20 cm

AC // BC = 26 cm

K = AB + BC + AC

K = 20 cm + 26 cm + 26 cm

K = 72 cm

b). Luas ∆segitiga ABC

DB = 10 cm, BC = 26 cm

Tinggi = DC , Teorema Pyhtaghoras :

DC² = BC² – DB²

DC² = 26² – 10²

DC² = 676 – 100

DC² = 576

DC = √576 = 24 cm

Luas segitiga :

alas = AD + DB = 10 + 10 = 20 cm

L = ½ × alas × tinggi

L = ½ × AB × DC

L = ½ × 20 × 24

L = 10 × 24

L = 240 cm²