The products of the slopes of perpendicular lines=_____?

Slopes are tangents of the angles of inclination. Product of slopes is tanθ tan(θ+90°) = tanθ(-cotθ) = -1 because tan and cot are reciprocals. This only fails when one of the lines is vertical (because that line has undefined slope).

-1

If neither of the lines is vertical, the product is -1.

yes

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## Answers

Slopes are tangents of the angles of inclination.

Product of slopes is tanθ tan(θ+90°) = tanθ(-cotθ) = -1

because tan and cot are reciprocals.

This only fails when one of the lines is vertical (because that line has undefined slope).

-1

If neither of the lines is vertical, the product is -1.

yes