Question

given the points A(0,0) ,B(4,3),C(2,9) what is the measure of < ABC?

Answer 1

let a=BC
b = AC
c = AB

find the length of each of the sides a, b, and c
the use the cosine law.
b^2 = a^2 + c^2 - 2ac cos B
solve for angle B

I will do one of the lengths,
a= √((2-4)^2 + 9-3)^2 ) = √(4+36) = √40

Answer 2

so would

b=the square root of 85 ?