What is the slope of a horizontal tangent line?

1 Answer

The slope of a horizontal tangent line is 0.

To calculate the slope of a straight line, we take a difference in the yy dimension and divide it by the change in the xx dimension of two points on the line:

"slope" = (y_1 - y_2)/(x_1 - x_2)slope=y1y2x1x2 assuming points (x_1, y_1)(x1,y1) and (x_2, y_2)(x2,y2) lie on the line

For a horizontal line y_1 - y_2 = 0y1y2=0 so

"slope" = 0/(x_1 - x_2) = 0slope=0x1x2=0