beserta caranya terimakasih..

AB / sinC = AC / sinB
10 / sinC = 15 / sin30°
10 / sinC = 15 / ½
15 sinC = 5
sinC = 5/15
sinC = ⅓

depan = 1
miring = 3
samping:
= √3² - 1²
= √9 - 1
= √8
= 2√2

cosC = samping / miring
cosC = 2√2 / 3
cosC = ⅔√2