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? asked in Science & MathematicsMathematics · 8 years ago

Calculus 2 Rectangular to polar?

Could someone please help me convert this rectangular equation to a polar equation?

x^2 + y^2 - 5px = 0

and also convert from Polar to rectangular.

r=7theta

Thanks in advance!

3 Answers

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    x = r * cos(t)

    y = r * sin(t)

    x^2 + y^2 = r^2

    x^2 + y^2 - 5px = 0

    r^2 - 5p * r * cos(t) = 0

    r - 5p * cos(t) = 0

    r = 5 * p * cos(t)

    Since

    x = r * cos(t)

    y = r * sin(t)

    Then it follows that

    (y/x) =>

    (r * sin(t)) / (r * cos(t)) =>

    sin(t)/cos(t) =>

    tan(t)

    Therefore

    t = arctan(y/x)

    r = 7t

    r^2 = 49t^2

    x^2 + y^2 = 49 * arctan(y/x)^2

    That's about as nice as it's going to get.

  • ?
    Lv 7
    8 years ago

    Taking your polar coords as {r, a} (Ican't type theta} x = rcosa, t = rsina; thatbchanges your equation to r^2cos^2a + r^2sin^2a - 5prcosa = 0; take out a common factor of r^2 to get r^2(cos^2 a + sin^2a) - 5prcos a = 0 or r^2 - 5prcos a = 0 - there are two or three variations on that you could write

    e.g. r^2= 5rpcos a etc. For the second one, x = rcos a, y = rsina so x =- 7acos a, y = 7asin a , but I don't see any way of rewriting that. In general, to convert either way, r = sqrt(x^2 + y^2), tan a = y/x .

    Source(s): Retired Maths Teacher
  • Anonymous
    5 years ago

    Multiply the two components via r,it follows that r^2=3rcosO replace r^2 via x^2 + y^2 and rcosO via x Then x^2+y^2=3x , so x^2-3x=-y^2 fixing for x: (x-3/2)^2=-y^2 via winding up the sq. (a-b)^2=a^2-2ab+b^2 and x-3/2=iy that's a complicated huge type, i being sqrt(-a million) x=3/2+iy, sturdy success

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