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Find the points of intersection for r = 3 + sin(theta) and r = 3 - sin(theta)!!!! PLEASE HELP!?

1. Find the points of intersection for r = 3 + sin(theta) and r = 3 - sin(theta).

PLEASE ANSWER LAST QUESTION

2. find the slope dy/dx of the polar curve r = 2 - 2cos(theta) at the point (r,theta) = (2, pi/2).

2 Answers

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  • r = 3 + sin(t)

    r = 3 - sin(t)

    3 + sin(t) = 3 - sin(t)

    2sin(t) = 0

    sin(t) = 0

    t = pi * k

    r = 3 + sin(pi * k)

    r = 3

    (3 , pi * k) where k is an integer

    r = 2 - 2cos(t)

    y = r * sin(t)

    x = r * cos(t)

    r * sin(t) =>

    2 * (1 - cos(t)) * sin(t) =>

    2sin(t) - sin(2t)

    y = 2sin(t) - sin(2t)

    dy/dt = 2cos(t) - 2cos(2t)

    r * cos(t) =>

    2 * (1 - cos(t)) * cos(t) =>

    2 * (cos(t) - cos(t)^2) =>

    2cos(t) - 2 * (1/2) * (1 + cos(2t)) =>

    2cos(t) - 1 - cos(2t)

    dx/dt =>

    -2sin(t) + 2sin(2t)

    dy/dx =>

    (dy/dt) / (dx/dt) =>

    (2cos(t) - 2cos(2t)) / (2sin(2t) - 2sin(t)) =>

    (cos(t) - cos(2t)) / (sin(2t) - sin(t))

    t = pi/2

    (cos(pi/2) - cos(pi)) / (sin(pi) - sin(pi/2)) =>

    (0 - (-1)) / (0 - 1) =>

    1/(-1) =>

    -1

  • 7 years ago

    1)we can also use polar co ordinate formula to avoid lengthy calculations.

    dr /d theta = 0 +2 sin theta ===> dtheta /dr = 1 / 2 sin theta = 1/ 2 * 2 sin( theta /2) cos( theta / 2)

    Attachment image
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