Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Homework Help: Does straight lines have slopes of tanget?

  1. Oct 23, 2004 #1
    Does straight lines have slopes of tangent?

    Does straight lines have slopes of tangent?.. :confused: i had no clue when this question came on a test..so i just left it...do they?..i just thought maybe they didn't since they have no limit. Hope i get an answer for this question.

    Last edited: Oct 23, 2004
  2. jcsd
  3. Oct 23, 2004 #2
    A straight line has the equation

    [tex]y = mx + c[/tex]

    here m is called its slope and c is the y-intercept. If you do not know, then this is a formula relating the y-coordinate of a point on the line to its x-coordinate (remember there must be a specific relationship between the x and y coordinates of a point if it moves on a well defined non-arbitrary curve...in this case the curve is a straight line).

    A straight line does have a tangent also called its slope. The important thing is that the slope of a straight line is constant (unlike that of other curves which may change from point to point...draw a diagram of a circle to convince yourself that this is so). Secondly, only two parameters are required to fix a straight line:

    1. Two points or
    2. One point and the slope
    3. Slope and y-intercept

    The more general equation of a straight line in the cartesian plane is

    ax + by + c = 0

    but as you can see, it can be transformed into the form mentioned above using simple algebraic manipulations.

  4. Oct 23, 2004 #3


    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member

    Every line is its own tangent line at each of its points.
  5. Oct 23, 2004 #4


    User Avatar
    Science Advisor

    I think what you mean is this: the slope of a straight line is the tangent of the angle the line makes with the x-axis. That is true.
  6. Oct 23, 2004 #5
    Thank u guys!!!! I understand much better now..i wish i had asked this question before the test ..oh well.. anyways Thank u

Share this great discussion with others via Reddit, Google+, Twitter, or Facebook