Imagine we drew a line from the centre (2,0) to the point (0,4).
Essentially the line we drew from the centre to that point on the circle is perpendicular to the tangent line slope-wise.
The slope of that line from the centre to the point is -2 based on the slope's equation or formula.
slope =
![(y2-y1)/(x2-x1)=(4-0)/(0-2) =-2](https://img.qammunity.org/2023/formulas/mathematics/high-school/p4li000ni3v069ilg992libgu6jcoicsey.png)
Therefore the tangent equation's slope is 1/2 since any perpendicular line's slope is the negative reciprocal of the original line's slope.
By using the point-slope form, we must have the point on the tangent plane (0,4) and the slope we found which is 1/2.
![y - 4 = (1)/(2)(x-0)\\ y= (1)/(2)x + 4](https://img.qammunity.org/2023/formulas/mathematics/high-school/dc3syxozqt9803kqaywh8ebonc1afhoac3.png)
Hope that helps!