Question

∆ABC
a=18,b=24,C=30 find cos B

Answer 1

(a)^2+(b)^2

=(18)^2+(24)^2

=324+576

=900

=(30)^2

=(c)^2

So,(a)^2+(b)^2=(c)^2

So ∆ABC is right angled at the angle between a and b which is angle B

Now,

CosB=Base/Hypothenuse

=b/c

=24/30

=4/5 or 0.8