dibantu ya Kak... poinnya besar lho

Aturan Cosinus

2.
cos C =  (a²+b² - c²)/(2 ab)
cos C = (25 +9 -16)/ (2)(5)(3)
cos C = 18/30= 3/5
<C = arc cos (3/5)= 53°

3. p  = 3, q = 7, r = 5
cos Q = (p² + r² - q²)/(2 pr)
cos Q = (9+25 - 49)/(2.3.5) =-15/30 = -1/2
<Q = arc cos(-1/2) = 120°

4. k = 2, l = 3, m  =2
cos K = (l²+m² - k²)/ (2 lm)
cos K = (9+4-4)/(2.3.2) =  9/12 = 3/4
<K = arc cos (3/4) = 41,4°