What is the slope of a horizontal tangent line?

1 Answer
Kuba Dolecki · Calculus V. · Amory W.
Jul 23, 2014

The slope of a horizontal tangent line is 0.

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

"slope" = (y_1 - y_2)/(x_1 - x_2) assuming points (x_1, y_1) and (x_2, y_2) lie on the line

For a horizontal line y_1 - y_2 = 0 so

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

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