Question about the direction of a vector

[Sall1230]

Homework Statement

Let A= 3i - 6j and B= 4i - 5j. The direction of the vector C = A - B is at an angle of?

Homework Equations

Magnitude= ( a^2 + b^2 ) ^1/2
Tan^-1 = b/a

The Attempt at a Solution

A-B =
3-4 i -6--5j
-1i -1j
Tan^-1 = -1/-1 = 45
45+180 = 225

Is this correct?

 

[Orodruin]

A-B =
3-4 i -6--5j
-1i -1j
Tan^-1 = -1/-1 = 45
45+180 = 225

Is this correct?

You really need to work on your notation here, the first line is missing parentheses or basis vectors for two terms, there is no equality sign between the second line and the third line, the inverse tangent function has no argument and -1/-1 is 1 and not 45.

That being said, what you are actually doing (which is not what you are writing) is correct.

 

[CWatters]

As this is a 2D problem it's not hard to draw it.