Question

Find the interior angle formed by points A(1,5,3) , B(-2,3,7) , C(3,2,5).

does this mean i need to find all the 3 angles of triangle?

Answer 1

I assume they mean find angle ABC

I would find vector BA
then find vector BC

then use either dot or cross product, dot product might be easier

BA dot BC = |BA| |BC| cos (ABC)
solve for ABC