Last updated at March 2, 2017 by Teachoo

Transcript

Ex 10.5, 6 ABCD is a cyclic quadrilateral whose diagonals intersect at a point E. If ∠DBC = 70°, ∠BAC is 30°, find ∠BCD. Further, if AB = BC, find ∠ECD. For segment DCBAD ∠ CBD & ∠ CAD are in the same segment So, they must be equal ∴ ∠ CAD = ∠ CBD ∴ ∠ CAD = 70° Also, ∠BAD = ∠BAC + ∠CAD ∠BAD = 30° + 70° ∠BAD = 100° Now, ABCD is a cyclic quadrilateral ∠BCD + ∠BAD = 180° ∠BCD + 100° = 180° ∠BCD = 180° – 100° ∠ BCD = 80° Also, if AB = BC, we need to find ∠ ECD In ∆ ABC, AB = BC So, ∠ BCA = ∠ BAC ∴ ∠ BCA = 30° Also, ∠ BCD = ∠ BCA + ∠ ECD 80° = 30° + ∠ ECD ∠ ECD = 80° – 30° ∠ ECD = 50°

Class 9

Important Questions for Exam - Class 9

- Chapter 1 Class 9 Number Systems
- Chapter 2 Class 9 Polynomials
- Chapter 3 Class 9 Coordinate Geometry
- Chapter 4 Class 9 Linear Equations in Two Variables
- Chapter 5 Class 9 Introduction to Euclid's Geometry
- Chapter 6 Class 9 Lines and Angles
- Chapter 7 Class 9 Triangles
- Chapter 8 Class 9 Quadrilaterals
- Chapter 9 Class 9 Areas of parallelograms and Triangles
- Chapter 10 Class 9 Circles
- Chapter 11 Class 9 Constructions
- Chapter 12 Class 9 Herons Formula
- Chapter 13 Class 9 Surface Areas and Volumes
- Chapter 14 Class 9 Statistics
- Chapter 15 Class 9 Probability

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Davneet Singh is a graduate from Indian Institute of Technology, Kanpur. He has been teaching from the past 7 years. He provides courses for Mathematics and Science from Class 6 to 12. You can learn personally from here https://www.teachoo.com/premium/maths-and-science-classes/.