What is it Asking; need to understand the concept please

When we have to determine the angle at which two lines intercept, the ONLY thing we have to know is the slope of each line .
Once we have those, we are able to determine the length of the angles at the point of intersection. Those angles are fixed and do not change, hence A is ans
My qustion from experts is the if we were asked the measure of the angle, how to find that

[email protected] wrote:If lines y=mx+b and x=y+bm intersect at a degrees angle (where a<90 ), what is the value of angle a ?

(1) m=2

(2) m=b

y = mx + b_________________(1)
x = y + bm
y = x - bm_________________(2)

Slope of line (2) = 1 => the line is at 45 degrees with respect to the horizontal axis.
Slope of line (1) = m

Statement 1: m = 2
Slope of line (1) can be found out. So the angle between the 2 lines can be found out.
Sufficient.

Statement 2: m = b
Slope of line (1) is unknown. Hence angle between the lines is unkown.
Not sufficient.

Choose A