Question

Segitiga abc dengan ab=6cm,
bc=10cm, dan ac=12cm. tentukan:
a. nilai cos sudut c
b. luas segitiga abc

Answer 1

A.)
cos c
= [bc²+ac²-ab²]/[2.bc.ac]
= [10²+12²-6²]/[2.10.12]
= [100+144-36]/240
= 208/240
= 13/15

Sehingga,
sin c = √(15²-13²)/15
sin c = √56 /15 = 2/15 √14
Didapat:
b.)
Luas:
= 1/2 ac.bc.sin c
= 1/2 10.12.2/15 √14
= 60. 2/15 √14
= 8√14 cm²