Home
Class 14
MATHS
ABC is a cyclic triangle and the bisecto...

ABC is a cyclic triangle and the bisectors of `angle BAC, angle ABC and angle BCA` meet the circle at P,Q and R respectively. Then the angle `angle RQP` is:

A

`90^(@)-(angleB)/(2)`

B

`90^(@)+(angleB)/(2)`

C

`90^(@)+(angleC)/(2)`

D

`90^(@)+(angleB)/(2)`

Text Solution

AI Generated Solution

The correct Answer is:
To solve the problem, we need to find the angle \( \angle RQP \) in the cyclic triangle \( ABC \) where the angle bisectors of \( \angle BAC, \angle ABC, \) and \( \angle BCA \) meet the circumcircle at points \( P, Q, \) and \( R \) respectively. ### Step-by-Step Solution: 1. **Understanding the Configuration**: - Since \( ABC \) is a cyclic triangle, all vertices \( A, B, C \) lie on a circle. The angle bisectors of the angles \( A, B, \) and \( C \) will intersect the circumcircle at points \( P, Q, R \). 2. **Using the Properties of Cyclic Triangles**: - In a cyclic triangle, the opposite angles sum up to \( 180^\circ \). This property will be useful in our calculations. 3. **Identifying Angles**: - Let \( \angle BAC = A \), \( \angle ABC = B \), and \( \angle BCA = C \). - The angles at points \( P, Q, R \) can be expressed in terms of \( A, B, \) and \( C \): - \( \angle BAP = \frac{A}{2} \) (since \( P \) is on the angle bisector of \( A \)) - \( \angle ABQ = \frac{B}{2} \) - \( \angle ACR = \frac{C}{2} \) 4. **Finding \( \angle RQP \)**: - To find \( \angle RQP \), we can use the fact that \( \angle RQP \) is the exterior angle for triangle \( AQR \): \[ \angle RQP = \angle AQR + \angle ARQ \] - Using the inscribed angle theorem, we know: \[ \angle AQR = \frac{1}{2} \angle A \quad \text{and} \quad \angle ARQ = \frac{1}{2} \angle B \] - Therefore: \[ \angle RQP = \frac{1}{2} A + \frac{1}{2} B \] 5. **Relating to Angle \( C \)**: - Since \( A + B + C = 180^\circ \), we can express \( C \) as: \[ C = 180^\circ - (A + B) \] - Thus: \[ \angle RQP = \frac{1}{2} (A + B) = \frac{1}{2} (180^\circ - C) = 90^\circ - \frac{C}{2} \] 6. **Final Result**: - Therefore, we conclude that: \[ \angle RQP = 90^\circ - \frac{C}{2} \] ### Conclusion: The angle \( \angle RQP \) in the cyclic triangle \( ABC \) where the angle bisectors meet the circumcircle at points \( P, Q, R \) is given by \( 90^\circ - \frac{C}{2} \).
Promotional Banner

Topper's Solved these Questions

  • GEOMETRY

    ADVANCED MATHS BY ABHINAY MATHS ENGLISH|Exercise QUESTIONS|158 Videos
  • LCM & HCF

    ADVANCED MATHS BY ABHINAY MATHS ENGLISH|Exercise MULTIPLE CHOICE QUESTIONS |140 Videos

Similar Questions

Explore conceptually related problems

In a Delta ABC , angle bisector of angle A, angle B & angle C cuts circumcircle at P, Q , R respectively . If angle CRQ=46^(@)& angle A=50^(@) , then find angle BQR .

If the bisector of angle A of the triangle ABC . makes an angle theta with BC, then sin theta=

In a triangle ABC , OB and OC are the bisector of angle angleB and angleC respectively . angleBAC = 60^@ . The angle angleBOC will be :

In Delta ABC , the bisector of angle B meets AC at D. A line PQ||AC meets AB,BC and BD at P,Q and R respectively. Show that BPxxQR=BQxxPR .

In triangle ABC , angle C is the greatest angle , then

ADVANCED MATHS BY ABHINAY MATHS ENGLISH-GEOMETRY TRIANGLES-QUESTIONS
  1. In a Delta ABC, angle A=65^(@), angle C=75^(@), where O is circumcentr...

    Text Solution

    |

  2. Find the circumradius of Delta ABC in which angle A=45^(@) side a=8sqr...

    Text Solution

    |

  3. ABC is a cyclic triangle and the bisectors of angle BAC, angle ABC and...

    Text Solution

    |

  4. In a triangle ABC, the lengths of the sides AB and AC equal to 17.5 cm...

    Text Solution

    |

  5. In a triangle ABC, AB=17 cm, AC=9cm, AD is perpendicular on BC and AD=...

    Text Solution

    |

  6. Perimeter of a Delta is 32 cm & inradius is 3 cm. Find the area of Del...

    Text Solution

    |

  7. Find the ratio of circumradius to inradius . If the ratio of sides is...

    Text Solution

    |

  8. The sides of a Delta are consecutive intergers and inradius is 4 cm. F...

    Text Solution

    |

  9. In a Delta ABC, I is incenter, angle BIC=116^(@) find angle A.

    Text Solution

    |

  10. O is the incentre of Delta ABC and angle A=30^(@), then find angle BOC...

    Text Solution

    |

  11. I is the incentre of Delta ABC, angle ABC=60^(@) and angle ACB=50^(@)....

    Text Solution

    |

  12. Let O be the in-centre of a triangle ABC and D be a point on the side ...

    Text Solution

    |

  13. In a Delta ABC, angle bisector of angle A, angle B & angle C cuts circ...

    Text Solution

    |

  14. In a DeltaABC, AD is angle bisector , AB=7 cm , AC=8 cm, BC=6cm, If I ...

    Text Solution

    |

  15. If the circumradius of a triangle is 7 cm and inradius is 3 cm . Find ...

    Text Solution

    |

  16. I and O are incentre and circumcentre of a Delta ABC. AI is produced a...

    Text Solution

    |

  17. In a Delta ABC, angleBOC=130^(@), if O is orthocentre . Find angle A.

    Text Solution

    |

  18. If the lengths of the sides of a triangle are in the ratio 4:5:6 and t...

    Text Solution

    |

  19. In a Delta ABC, AB=10 cm, BC=12 and AC=18 cm. Find the length of small...

    Text Solution

    |

  20. O is the Ortho centre of Delta ABC then A will be Orthocentre

    Text Solution

    |