NIMCET 2023 Mathematics PYQ — A circle touches the X -axis and also touches the circle with cen… | Mathem Solvex | Mathem Solvex
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NIMCET 2023 — Mathematics PYQ
NIMCET | Mathematics | 2023
A circle touches the X -axis and also touches the circle with centre (0,3) and radius 2. The locus of the centre of the circle is
Choose the correct answer:
A.
a circle
B.
An ellipse
C.
a parabola
(Correct Answer)
D.
a hyperbola
Correct Answer:
a parabola
Explanation
CONCEPT: When two circles having radius r1 and r2 and centers at C1 and C2 respective touches each other then ∣C1C2∣=r1+r2
CALCULATION: Let C1(h,k) be the center of the circle. ∴ Circle touches the x-axis then its radius is r1=k.
Also, the circle with centre C1 touches the another circle with centre C2(0,3) and radius r2=2.
∴∣C1C2∣=r1+r2 <br>⇒(h−0)2+(k−3)2=∣k+2∣<br> On Squaring both the sides of the above equation we get <br>⇒h2−10k+5=0<br> Now replace h with x and k with y in the above equation we get ⇒ Locus is x2−10y+5=0, which is parabola.
Therefore, option (1) is the correct answer.
Explanation
CONCEPT: When two circles having radius r1 and r2 and centers at C1 and C2 respective touches each other then ∣C1C2∣=r1+r2
CALCULATION: Let C1(h,k) be the center of the circle. ∴ Circle touches the x-axis then its radius is r1=k.
Also, the circle with centre C1 touches the another circle with centre C2(0,3) and radius r2=2.
∴∣C1C2∣=r1+r2 <br>⇒(h−0)2+(k−3)2=∣k+2∣<br> On Squaring both the sides of the above equation we get <br>⇒h2−10k+5=0<br> Now replace h with x and k with y in the above equation we get ⇒ Locus is x2−10y+5=0, which is parabola.
Therefore, option (1) is the correct answer.
NIMCET
The equation 3x2+10xy+11y2+14x+12y+5=0 represents,