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Circle on which the co-ordinates of any ...

Circle on which the co-ordinates of any point are `{2+4cos theta, -1+4 sin theta}` where `theta` is parameter is `(x-2)^(2)+(y+1)^(2)=16`.

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To solve the problem, we need to show that the parametric coordinates given by \( (2 + 4 \cos \theta, -1 + 4 \sin \theta) \) represent a circle and that this circle is described by the equation \( (x - 2)^2 + (y + 1)^2 = 16 \). ### Step-by-Step Solution: 1. **Identify the parametric equations**: - Given the coordinates: \[ x = 2 + 4 \cos \theta \] \[ y = -1 + 4 \sin \theta \] 2. **Rearrange the equations**: - Rearranging for \( \cos \theta \) and \( \sin \theta \): \[ x - 2 = 4 \cos \theta \quad \text{(1)} \] \[ y + 1 = 4 \sin \theta \quad \text{(2)} \] 3. **Square both equations**: - Squaring both sides of equations (1) and (2): \[ (x - 2)^2 = (4 \cos \theta)^2 = 16 \cos^2 \theta \quad \text{(3)} \] \[ (y + 1)^2 = (4 \sin \theta)^2 = 16 \sin^2 \theta \quad \text{(4)} \] 4. **Add the squared equations**: - Adding equations (3) and (4): \[ (x - 2)^2 + (y + 1)^2 = 16 \cos^2 \theta + 16 \sin^2 \theta \] 5. **Use the Pythagorean identity**: - We know from trigonometry that \( \cos^2 \theta + \sin^2 \theta = 1 \): \[ 16 \cos^2 \theta + 16 \sin^2 \theta = 16(1) = 16 \] 6. **Final equation**: - Therefore, we have: \[ (x - 2)^2 + (y + 1)^2 = 16 \] 7. **Conclusion**: - This is the equation of a circle with center at \( (2, -1) \) and radius \( 4 \) (since \( \sqrt{16} = 4 \)). Thus, the parametric coordinates indeed represent the same circle described by the equation \( (x - 2)^2 + (y + 1)^2 = 16 \).
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Knowledge Check

  • The locus of the point whose co-ordinates are x = 3 cos theta + 2 , y = 3 sin theta - 4 , where theta is a parameter , is

    A
    circle
    B
    parabola
    C
    ellipse
    D
    hyperbola
  • If the coordinates of a variable point be (cos theta + sin theta, sin theta - cos theta) , where theta is the parameter, then the locus of P is

    A
    `x^(2)-y^(2)=4`
    B
    `x^(2)+y^(2)=2`
    C
    xy = 3
    D
    `x^(2)+2y^(2)=3`
  • The length of the chord joining the points (4cos theta, 4sin theta) and [4cos(theta+60^(@)), 4 sin(theta+60^(@))] of the circle x^(2)+y^(2)=16 is

    A
    4
    B
    6
    C
    2
    D
    8
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