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Determine the equation of the circle with diameter NP, where N(-2; 3) and P(4; -7). Then, find the equation of the tangent to the circle at point N.

Mathematics

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Answer

(x−1)2+(y+2)2=34(x - 1)^2 + (y + 2)^2 = 34

y=35x+215y = \frac{3}{5}x + \frac{21}{5}

NP^Q≈31.0∘N\hat{P}Q \approx 31.0^\circ

Step-by-step solution

5 steps
  1. Determine the center and radius of the circle (for 4.1)

    The diameter of the circle is NP, with N(−2;3)(-2; 3) and P(4;−7)(4; -7).
    The center of the circle (a;b)(a; b) is the midpoint of the diameter NP.

    a=xN+xP2=−2+42=22=1a = \frac{x_N + x_P}{2} = \frac{-2 + 4}{2} = \frac{2}{2} = 1 b=yN+yP2=3+(−7)2=−42=−2b = \frac{y_N + y_P}{2} = \frac{3 + (-7)}{2} = \frac{-4}{2} = -2

    The center of the circle is (1;−2)(1; -2).

    The radius squared, r2r^2, can be found using the distance from the center (1;−2)(1; -2) to N(−2;3)(-2; 3).

    r2=(xN−a)2+(yN−b)2r^2 = (x_N - a)^2 + (y_N - b)^2 r2=(−2−1)2+(3−(−2))2r^2 = (-2 - 1)^2 + (3 - (-2))^2 r2=(−3)2+(5)2r^2 = (-3)^2 + (5)^2 r2=9+25r^2 = 9 + 25 r2=34r^2 = 34
  2. Write the equation of the circle (for 4.1)

    Using the center (a;b)=(1;−2)(a; b) = (1; -2) and r2=34r^2 = 34, the equation of the circle is:

    (x−a)2+(y−b)2=r2(x - a)^2 + (y - b)^2 = r^2 (x−1)2+(y−(−2))2=34(x - 1)^2 + (y - (-2))^2 = 34 (x−1)2+(y+2)2=34\boxed{(x - 1)^2 + (y + 2)^2 = 34}
  3. Determine the equation of the tangent at N (for 4.2)

    The tangent to the circle at N(−2;3)(-2; 3) is perpendicular to the radius CN, where C is the center (1;−2)(1; -2).
    First, calculate the gradient of the radius CN:

    mCN=yN−yCxN−xC=3−(−2)−2−1=5−3=−53m_{CN} = \frac{y_N - y_C}{x_N - x_C} = \frac{3 - (-2)}{-2 - 1} = \frac{5}{-3} = -\frac{5}{3}

    The gradient of the tangent line, mtangentm_{tangent}, is the negative reciprocal of mCNm_{CN}:

    mtangent=−1mCN=−1−53=35m_{tangent} = -\frac{1}{m_{CN}} = -\frac{1}{-\frac{5}{3}} = \frac{3}{5}

    Now, use the point-slope form y−y1=m(x−x1)y - y_1 = m(x - x_1) with N(−2;3)(-2; 3) and mtangent=35m_{tangent} = \frac{3}{5}:

    y−3=35(x−(−2))y - 3 = \frac{3}{5}(x - (-2)) y−3=35(x+2)y - 3 = \frac{3}{5}(x + 2) y−3=35x+65y - 3 = \frac{3}{5}x + \frac{6}{5} y=35x+65+3y = \frac{3}{5}x + \frac{6}{5} + 3 y=35x+65+155y = \frac{3}{5}x + \frac{6}{5} + \frac{15}{5} y=35x+215\boxed{y = \frac{3}{5}x + \frac{21}{5}}
  4. Calculate the size of NP^QN\hat{P}Q (for 4.3)

    Given N(−2;3)(-2; 3), P(4;−7)(4; -7), and Q(4;3)(4; 3). NP is the diameter.
    An angle subtended by a diameter at any point on the circumference is 90∘90^\circ. Therefore, NQ^P=90∘N\hat{Q}P = 90^\circ.
    This means △NPQ\triangle NPQ is a right-angled triangle at Q.
    Calculate the lengths of the sides NQ and PQ:

    NQ=(xQ−xN)2+(yQ−yN)2=(4−(−2))2+(3−3)2=(6)2+(0)2=36=6NQ = \sqrt{(x_Q - x_N)^2 + (y_Q - y_N)^2} = \sqrt{(4 - (-2))^2 + (3 - 3)^2} = \sqrt{(6)^2 + (0)^2} = \sqrt{36} = 6 PQ=(xQ−xP)2+(yQ−yP)2=(4−4)2+(3−(−7))2=(0)2+(10)2=100=10PQ = \sqrt{(x_Q - x_P)^2 + (y_Q - y_P)^2} = \sqrt{(4 - 4)^2 + (3 - (-7))^2} = \sqrt{(0)^2 + (10)^2} = \sqrt{100} = 10

    In the right-angled triangle △NPQ\triangle NPQ, we can use trigonometry to find NP^QN\hat{P}Q:

    tan⁡(NP^Q)=oppositeadjacent=NQPQ=610=35\tan(N\hat{P}Q) = \frac{\text{opposite}}{\text{adjacent}} = \frac{NQ}{PQ} = \frac{6}{10} = \frac{3}{5} NP^Q=arctan⁡(35)N\hat{P}Q = \arctan\left(\frac{3}{5}\right) NP^Q≈30.9637∘N\hat{P}Q \approx 30.9637^\circ

    Rounding to one decimal place:

    NP^Q≈31.0∘\boxed{N\hat{P}Q \approx 31.0^\circ}
  5. Calculate the value of Area of △PQNArea of the circle\frac{\text{Area of } \triangle PQN}{\text{Area of the circle}} (for 4.4)

    First, calculate the area of △PQN\triangle PQN. Since it's a right-angled triangle at Q:

    Area of △PQN=12×base×height=12×PQ×NQ\text{Area of } \triangle PQN = \frac{1}{2} \times \text{base} \times \text{height} = \frac{1}{2} \times PQ \times NQ
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