205 — 210

BC = c = 13

AB + AC = a + b = 17

r = 17 — 13 / 2 = 2

P = 36
BC = c = 15

AB = AC = 36 — 15 = 21

r = 21 — 15 / 2 = 3

<ABC = 80o
<AOC — ?

50 + <O = 180

<O = x + O + y = 180

2x + 80 + 2y = 180

2x + 2y = 100

2(x + y) = 100

x + y = 50

<C = 120o
AC = BC = a

<A = <B = 180 — 120 / 2 = 30o

<OCB = 120:2 = 60o

<OCB = <OBC = 60o

R = a

R = a * b * c / 4 * S

CH = a/2

AH2 = a2/1 — a2/4 = 4a2 — a2 / 4 = 3a2/4

AH = √3a2/4 = a√3/2

AB = a√3

S = a√3 * a/2 / 2 = a2√3/2 * 1/2 = a2√3/4

a2√3/4 * 4 = a2√3

AB = CD
BC = 2
AD = 8
P — ?

BC + AD = AB + CD = 10

P = 20