# Construction 11.1 - Chapter 11 Class 9 Constructions

Last updated at Oct. 5, 2018 by Teachoo

Last updated at Oct. 5, 2018 by Teachoo

Transcript

Construction 11.1 : To construct the bisector of a given angle. Given an angle ABC, we want to construct is bisector Steps of Construction: 1. Draw an arc of any radius intersecting BA and BC at points E & D 2. Next, taking D and E as centers and with the radius more than 1/2 DE, draw arcs to intersect each other. 3. Mark the point as F. 4. Join BF So, BF is the bisector of the ∠ ABC. Justification We have to prove BF bisects ∠ ABC, i.e. we have to prove ∠ EBF = ∠ DBF Join DF and EF. In Δ BEF and Δ BDF, BE = BD EF = DF BF = BF ∴ ∆BEF ≅ ∆BDF ∴ ∠ EBF = ∠ DBF Thus, BF is bisector of ∠ ABC

Constructing bisector of angle and perpendicular bisector

Chapter 11 Class 9 Constructions

Concept wise

- Constructing bisector of angle and perpendicular bisector
- Constructing angles - 60, 90, 45, 30 and others
- Constructing Triangle - Given base, angle and sum of other 2 sides
- Constructing Triangle - Given base, angle and difference of sides
- Constructing Triangle - Given sum of 3 sides and 2 base angles

About the Author

Davneet Singh

Davneet Singh is a graduate from Indian Institute of Technology, Kanpur. He has been teaching from the past 9 years. He provides courses for Maths and Science at Teachoo.