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# Name an **important source** from which naphthalene balls are obtained.

Naphthalene balls used to repel moths and other insects are obtained from

**coal tar.**- Related Articles
- Naphthalene balls are obtained from coal tar and are used asmosquito repellanthoneybee repellantmoth repellantsnake repellant
- If \( P A \) and \( P B \) are tangents from an outside point \( P \). such that \( P A=10 \mathrm{~cm} \) and \( \angle A P B=60^{\circ} \). Find the length of chord \( A B \).
- From an external point \( P \), tangents \( P A=P B \) are drawn to a circle with centre \( O \). If \( \angle P A B=50^{\circ} \), then find \( \angle A O B \).
- Name the source from which nitrogen and oxygen are obtained on a large scale.
- From a point \( P \), two tangents \( P A \) and \( P B \) are drawn to a circle with centre \( O \). If \( O P= \) diameter of the circle, show that \( \Delta A P B \) is equilateral.
- From an external point \( P \), tangents \( P A \) and \( P B \) are drawn to a circle with centre \( O \). At one point \( E \) on the circle tangent is drawn, which intersects \( P A \) and \( P B \) at \( C \) and \( D \) respectively. If \( P A=14 \mathrm{~cm} \), find the perimeter of \( \triangle P C D \).
- Two tangent segments \( P A \) and \( P B \) are drawn to a circle with centre \( O \) such that \( \angle A P B=120^{\circ} . \) Prove that \( O P=2 A P \).
- In the figure, there are two concentric circles with centre \( O \) of radii \( 5 \mathrm{~cm} \) and \( 3 \mathrm{~cm} \). From an external point \( P \), tangents \( P A \) and \( P B \) are drawn to these circles. If \( A P=12 \mathrm{~cm} \), find the length of \( B P \)."\n
- In the figure, \(P A \) and \( P B \) are tangents from an external point \( P \) to a circle with centre \( O \). \( L N \) touches the circle at \( M \). Prove that \( P L+L M=P N+M N \)."\n
- Give expressions for the following cases. (a) 7 added to \( p \)(b) 7 subtracted from \( p \)
- In the figure, \( P A \) and \( P B \) are tangents to the circle from an external point \( P \). \( C D \) is another tangent touching the circle at \( Q \). If \( PA=12\ cm, QC=QD=3\ cm, \) then find \( P C+P D \)."\n
- Name the source from which litmus solution is obtained. What is the use of this solution?
- p>Match the acids given in Column (A) with their correct source given in Column (B):
- Find the value of:(a) \( 4.9 \p 0.07 \)(b) \( 26.4 \p 2.4 \)
- A point $A( 0,\ 2)$ is equidistant from the points $B( 3,\ p)$ and $C( p,\ 5)$, then find the value of P.

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