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Example 3 - Consider ACB, AB = 29, BC = 21 and angle ABC - Concept wise

Example 3 - Chapter 8 Class 10 Introduction to Trignometry - Part 2
Example 3 - Chapter 8 Class 10 Introduction to Trignometry - Part 3

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Example 3 - Chapter 8 Class 10 Introduction to Trignometry - Part 4

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Example 3 Consider ACB, right-angled at C, in which AB = 29 units, BC = 21 units and ABC = (see fig.). Determine the values of (i) cos2 + sin2 , Step1 : Finding sides of triangle In right triangle ABC, using Pythagoras theorem (Hypotenuse)2 = (Height)2 + (Base)2 AB2 = AC2 + BC2 AC2 = AB2 BC2 AC2 = (29)2 (21)2 Using a2 b2 = (a + b) (a b) AC2 = (29 21) (29 + 21) AC2 = (8) (50) AC = (8 50) AC = 400 AC = 20 Step 2 : Finding sin , cos We have to find out , cos2 + sin2 Putting values = (21/29)^2+(20/29)^2 = ((21)2 + (20)2)/292 = (441 + 400)/841 = 841/841 = 1 So, cos2 + sin2 = 1 Example 3 Consider ACB, right-angled at C, in which AB = 29 units, BC = 21 units and ABC = (see fig.). Determine the values of (ii) cos2 sin2 . cos2 sin2 Putting values = (21/29)^2 (20/29)^2 = ((21)2 (20)2)/292 Using a2 b2 = (a + b) (a b) = ((21 + 20)(21 20))/292 = ((41)(1))/841 = 41/841

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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.