Sorry I’m only answering this so I can ask
Here, I've attached a picture of the triangle that accompanies this explanation.
cot = = =
Now view the triangle.
PS. Angle theta will have a coordinate of (-, +) because it is in quadrant II.
sin of the angle would be opposite/hypotenuse, so sin =
cos of the angle would be adjacent/hypotenuse, so cos =
tan of the angle would be opposite/adjacent, so tan =
It’s the point where the parabola crosses its axis of symmetry
For this case we have that by definition, the equation of a line of the slope-intersection form is given by:

Where:
m: It's the slope
b: It is the cut-off point with the y axis
While the point-slope equation of a line is given by:

Where:
m: It's the slope
It is a point through which the line passes
In this case we have a line through:
(8,4) and (0,2)
Therefore, its slope is:

Its point-slope equation is:

Then, we manipulate the expression to find the equation of the slope-intersection form:

Therefore, the cut-off point with the y-axis is 
ANswer:
