Slope of Lines
Date: 8/6/96 at 21:34:25 From: Anonymous Subject: Slope of Lines i) What is the slope of the line y = -px + 5 if the line goes through (0, -3)? ii) Why does the y-axis have an infinite slope, and the x-axis have a slope of 0?
Date: 8/7/96 at 9:19:6 From: Doctor Anthony Subject: Re: Slope of Lines (i) The gradient [slope] is the value of -p in your equation. Substitute (0, -3) for x and y in the equation, and we get -3 = -p(0) + 5 This is clearly not possible unless p is infinite. The line is in fact the y axis, as can be seen from the fact that it goes through (0, 5) and (0, -3), and the y axis has infinite gradient. (ii) The gradient of a line is the tangent of the angle of slope; that is, the tangent of the angle between the line and the positive x axis. The x axis has angle 0 with itself, so its gradient is tan(0) = 0. The y axis makes an angle of 90 degrees with the x axis, and tan(90) = infinity, So the y axis has infinite gradient. -Doctor Anthony, The Math Forum Check out our web site! http://mathforum.org/dr.math/
Search the Dr. Math Library:
Ask Dr. MathTM
© 1994- The Math Forum at NCTM. All rights reserved.