Plane Geometry
-  In a circle with centre O, AB is a chord, and AP is a tangent to the circle. If ∠AOB = 140°, then the measure of ∠PAB is
- 
                        View Hint View Answer Discuss in Forum According to question , we draw a figure of a circle with centre O ,  
 In ∆ OAB,
 Here , OA = OB = radius
 ∴ ∠OAB = ∠OBA
 ∴ ∠OAB + ∠OBA + ∠AOB = 180°
 ∴ 2∠OAB = 180° – 140° = 40°Correct Option: CAccording to question , we draw a figure of a circle with centre O ,  
 In ∆ OAB,
 Here , OA = OB = radius
 ∴ ∠OAB = ∠OBA
 ∴ ∠OAB + ∠OBA + ∠AOB = 180°
 ∴ 2∠OAB = 180° – 140° = 40°⇒ ∠OAB = 40 = 20° 2 
 ∴ ∠PAO = 90°
 ∴ ∠PAB = 90° – 20° = 70°
-  Two circles with radii 25 cm and 9 cm touch each other externally. The length of the direct common tangent is
- 
                        View Hint View Answer Discuss in Forum On the basis of question we draw a figure of two circles with radii 25 cm and 9 cm touch each other externally.  
 Here , r1 = 25 cm, r2 = 9 cm
 We find the required answer with the help of given formula ,
 Length of common tangent = √(distance between centres)² - (r1 - r2)²
 Length of common tangent = √(25 + 9)² - (25 - 9)²Correct Option: BOn the basis of question we draw a figure of two circles with radii 25 cm and 9 cm touch each other externally.  
 Here , r1 = 25 cm, r2 = 9 cm
 We find the required answer with the help of given formula ,
 Length of common tangent = √(distance between centres)² - (r1 - r2)²
 Length of common tangent = √(25 + 9)² - (25 - 9)²
 Length of common tangent = √(34)² - (16)²
 Length of common tangent = √(34 + 16)(34 - 16)
 Length of common tangent = √50 × 18 = 30 cm.
-  ST is a tangent to the circle at P and QR is a diameter of the circle. If ∠RPT = 50°, then the value of ∠SPQ is
- 
                        View Hint View Answer Discuss in Forum According to question , we draw a figure of a circle with centre O ,  
 Here , ∠RPT = 50°
 ∠RPQ = 90° (Angle of semi circle)Correct Option: AAccording to question , we draw a figure of a circle with centre O ,  
 Here , ∠RPT = 50°
 ∠RPQ = 90° (Angle of semi circle)
 ∠TPS = 180°
 ∴ ∠SPQ = 180° – 50° – 90° = 40°
-  The distance between the centres of two circles with radii 9 cm and 16 cm is 25 cm. The length of the segment of the tangent between them is
- 
                        View Hint View Answer Discuss in Forum On the basis of question we draw a figure of two circles with radii 9 cm and 16 cm ,  
 Given that , r1 = 9 cm and r2 = 16 cm
 Distance between two centres = 25 cm
 ∴ Required length of tangent = √(Distance between two centres)2 - (r1 - r2)2
 Required length of tangent = √(25)² - (16 -9)²Correct Option: AOn the basis of question we draw a figure of two circles with radii 9 cm and 16 cm ,  
 Given that , r1 = 9 cm and r2 = 16 cm
 Distance between two centres = 25 cm
 ∴ Required length of tangent = √(Distance between two centres)2 - (r1 - r2)2
 Required length of tangent = √(25)² - (16 -9)²
 Required length of tangent = √625 - 49
 Required length of tangent = √576 = 24 cm
-  DE is a tangent to the circumcircle of ∆ ABC at the vertex A such that DE|| BC. If AB = 17 cm, then the length of AC is equalto
- 
                        View Hint View Answer Discuss in Forum As per the given in question , we draw a figure  
 DE || BC
 ∴ ∠DAB = ∠ABC
 ∠EAC = ∠ACBCorrect Option: DAs per the given in question , we draw a figure  
 DE || BC
 ∴ ∠DAB = ∠ABC
 ∠EAC = ∠ACB
 Hence, ABC is equilateral triangle.
 ∴ side AB = AC = BC = 17 cm
 
	