Question : If two tangents to a circle of radius 3 cm are inclined to each other at an angle of 60°, then the length of each tangent is:
Option 1: $\frac{3 \sqrt{3}}{4} \mathrm{~cm}$
Option 2: $3 \sqrt{3} \mathrm{~cm}$
Option 3: $3 \mathrm{~cm}$
Option 4: $6 \mathrm{~cm}$
Correct Answer: $3 \sqrt{3} \mathrm{~cm}$
Solution : Let P be an external point, from where two tangents are drawn to the circle and the angle between them is 60°. Join OA and OP. OA = 3, is the radius of the circle. Also, OP is the bisector of $\angle$P. So, $\angle$APO = $\angle$CPO = 30° Since tangents at any point of a circle are perpendicular to the radius through the point of contact. So, OA $\perp$ AP From $\triangle$OPA, We get, $\tan 30°=\frac{OA}{AP}$ ⇒ $\frac{1}{\sqrt3}=\frac{3}{AP}$ $\therefore AP =3\sqrt3$ Tangents drawn from an external point are equal. So, AP = CP = $3\sqrt3\ \text{cm}$ Hence, the correct answer is $3\sqrt3\ \text{cm}$.
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Question : Find the area of a triangle whose length of two sides are 4 cm and 5 cm and the angle between them is 45°.
Option 1: $4 \sqrt{2} \mathrm{~cm}^2$
Option 2: $7 \sqrt{2} \mathrm{~cm}^2$
Option 3: $5 \sqrt{2} \mathrm{~cm}^2$
Option 4: $6 \sqrt{2} \mathrm{~cm}^2$
Question : Out of two concentric circles, the radius of the outer circle is 6 cm and the chord PQ of the length 10 cm is a tangent to the inner circle. Find the radius (in cm) of the inner circle.
Option 1: $4$
Option 2: $\sqrt{7}$
Option 3: $\sqrt{13}$
Option 4: $\sqrt{11}$
Question : $\triangle \mathrm{ABC}$ and $\triangle \mathrm{DEF}$ are two triangles such that $\triangle \mathrm{ABC} \cong \triangle \mathrm{FDE}$. If AB = 5 cm, $\angle$B = 40° and $\angle$A = 80°, then which of the following options is true?
Option 1: DF = 5 cm, $\angle$E = 60°
Option 2: DE = 5 cm, $\angle$F = 60°
Option 3: DE = 5 cm, $\angle$D = 60°
Option 4: DE = 5 cm, $\angle$E = 60°
Question : Two identical circles each of radius $2\;\mathrm{cm}$ intersect each other such that the circumference of each one passes through the centre of the other. What is the area (in $\mathrm{cm^2}$) of the intersecting region?
Option 1: $\frac{8\pi }{3}-2\sqrt{3}$
Option 2: $\frac{8\pi }{3}-\sqrt{3}$
Option 3: $\frac{4\pi }{3}-\sqrt{3}$
Option 4: $\frac{4\pi }{3}-2\sqrt{3}$
Question : In a circle with centre O, AD is a diameter and AC is a chord. Point B is on AC such that OB = 7 cm and $\angle OBA=60^{\circ}$. If $\angle \mathrm{DOC}=60^{\circ}$, then what is the length of BC?
Option 1: $3 \sqrt{7} \mathrm{~cm}$
Option 2: $3.5 \mathrm{~cm}$
Option 3: $7 \mathrm{~cm}$
Option 4: $5 \sqrt{7} \mathrm{~cm}$
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