39 dan 40 tolong di bantuin dong aku bingung, pakai cara juga ya

39]
a = 18 cm
b = 24 cm
c = 30 cm

R lingkaran luar segitiga = ...???

s = 1/2 (a + b + c)
s = 1/2 (18 + 24 + 30)
s = 1/2 (72)
s = 36 cm

L = V[s(s - a)(s - b)(s - c)]
L = V[36(36 - 18)(36 - 24)(36 - 30)]
L = V(36(18)(12)(6))
L = V(46656)
L = 216 cm^2

R = [(a)(b)(c)]/4(L)
R = [(18)(24)(30)]/4(216)
R = 12960/864
R = 15 cm (D)


40]
a = 3 cm
b = 4 cm
c = 5 cm

K lingkaran dalam segitiga = ...???

L = 1/2 × a × b
L = 1/2 × 3 × 4
L = 6 cm^2

s = 1/2 (a + b + c)
s = 1/2 (3 + 4 + 5)
s = 1/2 (12)
s = 6 cm

r = L/s
r = 6/6
r = 1 cm

K = 2 × phi × r
K = 2 × 3,14 × 1
K = 6,28 cm (B)