Check sibling questions

Ex 3.7, 5 (Optional) - In ABC, angle C = 3 B = 2 (A + B) - teachoo

Ex 3.7, 5 (Optional) - Chapter 3 Class 10 Pair of Linear Equations in Two Variables - Part 2
Ex 3.7, 5 (Optional) - Chapter 3 Class 10 Pair of Linear Equations in Two Variables - Part 3 Ex 3.7, 5 (Optional) - Chapter 3 Class 10 Pair of Linear Equations in Two Variables - Part 4

This video is only available for Teachoo black users

Maths Crash Course - Live lectures + all videos + Real time Doubt solving!


Transcript

Ex 3.7, 5 In a Δ ABC, ∠ C = 3 ∠ B = 2 (∠ A + ∠ B). Find the three angles. Let ∠A = x & ∠B = y Given that ∠C = 3 ∠B ∠ C = 3y Also, ∠ C = 2 (∠A + ∠B) ∠C = 2 (x + y) For ∠C = 3y Put ∠A = x ∠B = y and ∠C = 3y Since ABC is a triangle, By Angle Sum property ∠A + ∠B + ∠C = 180 x + y + 3y = 180 x + 4y = 180 For ∠C = 2(x + y) Put ∠A = x ∠B = y and ∠C = 2 (x + y) Since ABC is a triangle, By Angle Sum Property ∠A + ∠B + ∠C = 180 x + y + 2 (x + y) = 180 x + y + 2x + 2y = 180 3x + 3y = 180 3(x + y) = 180 (x + y) = 180/3 x + y = 60 Hence, the equations are x + 4y = 180 …(1) x + y = 60 …(2) From equation (1) x + 4y = 180 x = 180 − 4y Put x = 180 − 4y in equation (2) x + y = 60 180 − 4y + y = 60 180 − 60 = 4y − y 120 = 3y 3y = 120 y = 120/3 y = 40 Put y = 40° in equation (1) x + 4y = 180 x + (4 × 40) = 180 x + 160 = 180 x = 20 Thus, ∠ A = x = 20° ∠ B = y = 40° ∠C = 3y = 3 × 40 = 120°

Ask a doubt (live)
Davneet Singh's photo - Co-founder, Teachoo

Made by

Davneet Singh

Davneet Singh has done his B.Tech from Indian Institute of Technology, Kanpur. He has been teaching from the past 12 years. He provides courses for Maths, Science, Social Science, Physics, Chemistry, Computer Science at Teachoo.