What is the angle theta between vectors

[juggalomike]

Homework Statement

What is the angle theta between vectors vec A and vec B if vec A = 4 -3 and
vec B = -2 + 5?

Homework Equations

arccos((a dot b)/(|a||b|))

The Attempt at a Solution

4*-2+-3*5=-23
sqrt(4^2+-3^2)*sqrt(-2^2+5^2)=10.39

arc
not sure what i am doing wrong but that's the equation i found online and i keep getting undefined when i plug it into my calculator

 

[Doc Al]

Show what you plugged in.

 

[juggalomike]

edited the question, but sorry i realized my error, had a mistake in the magnitudes, got the problem right