jawab no 16,17 berserta caranya poin banyak

16
<PQR = 60
<PRQ = 75
<QPR = 180 - 60 - 75 = 45
sisi terpendek = QR
QR/sin <QPR = PR/sin <PQR
QR /sin 45 = PR/sin 60

QR = PR . sin 45/ sin 60
QR = 10√6 ( ¹/₂ √2) / (¹/₂ √3)
QR = 5√12 /(¹/₂ √3) = 10 √(12/3) = 10√4 = 20 cm

17.
a+b + c = 10
<B = 30
<C = 120
<A = 180 -30 - 120
<A = 30

krn <A = < B =30, maka ΔABC sama kaki
AC =  BC --> b = a

a+b + c = 10
a+a + c = 10
2a = 10 - c
a = 5 - 1/2 c

c/ sin C = a/sin A
c = a. sin C/ sin A
c = a. sin 120 / sin 30
c = a. (1/2√3)/ (1/2)
c =  a √3

c = (5 -1/2 c) √3
c = 5√3 - 1/2c√3
c + 1/2 c √3 =  5
c(1 + 1/2 √3) =  5
c= 5 / (1  + 1/2 √3) = 10/ (2 + √3)
c = 10(2 - √3)/ ( 1)
c = 20  - 10√3