Q68 / 150 · MHT CET 2025 (21 Apr Shift 2) · Mathematics
The locus of point of intersection of the tangents to the circle $x^2+y^2=16$, such that the angle between them is $60^{\circ}$, is
- A$x^2+y^2=4$
- Correct answerB$x^2+y^2=64$
- C$x^2+y^2=32$
- D$x^2+y^2=48$
Solution
The circle $x^2 + y^2 = 16$ has center at the origin and radius $4$. For two tangents from an external point $P(h, k)$ intersecting at $60^\circ$, the line from the center to $P$ bisects the angle between the tangents, making the angle between $OP$ and either tangent $30^\circ$.
In right triangle $\triangle OTP$, where $T$ is the point of tangency, $\sin 30^\circ = \frac{r}{OP} = \frac{4}{OP}$. Since $\sin 30^\circ = \frac{1}{2}$, we have $OP = 8$.
The distance $OP = \sqrt{h^2 + k^2} = 8$, so squaring both sides yields $h^2 + k^2 = 64$. Replacing $(h, k)$ with $(x, y)$ gives the locus $x^2 + y^2 = 64$.
Final answer: $\boxed{\text{B}}$
Hence, the correct answer is option: 'B'.