• wholookshere@lemmy.blahaj.zone
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    17 hours ago

    I’m saying that the tangent of a straight line in Cartesian coordinates, projected into polar, does not have constant tangent. A line with a constant tangent in polar, would look like a circle in Cartesian.

    • ltxrtquq@lemmy.ml
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      16 hours ago

      Polar Functions and dydx

      We are interested in the lines tangent a given graph, regardless of whether that graph is produced by rectangular, parametric, or polar equations. In each of these contexts, the slope of the tangent line is dydx. Given r=f(θ), we are generally not concerned with r′=f′(θ); that describes how fast r changes with respect to θ. Instead, we will use x=f(θ)cosθ, y=f(θ)sinθ to compute dydx.

      From the link above. I really don’t understand why you seem to think a tangent line in polar coordinates would be a circle.

      • wholookshere@lemmy.blahaj.zone
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        1 hour ago

        Sorry that’s not what I’m saying.

        I’m saying a line with constant tangent would be a circle not a line.

        Let me try another way, a function with constant first derivative in polar coordinates, would draw a circle in Cartesian

        • ltxrtquq@lemmy.ml
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          48 minutes ago

          Given r=f(θ), we are generally not concerned with r′=f′(θ); that describes how fast r changes with respect to θ

          I think this part from the textbook describes what you’re talking about

          Instead, we will use x=f(θ)cosθ, y=f(θ)sinθ to compute dydx.

          And this would give you the actual tangent line, or at least the slope of that line.