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Example 7 - From a point on a bridge across a river - Questions easy to difficult

Example 7 - Chapter 9 Class 10 Some Applications of Trigonometry - Part 2
Example 7 - Chapter 9 Class 10 Some Applications of Trigonometry - Part 3


Transcript

Example 7 From a point on a bridge across a river, the angles of depression of the banks on opposite sides of the river are 30 and 45 , respectively. If the bridge is at a height of 3 m from the banks, find the width of the river. Let the width of the river = AB And the bridge is at a height of 3m from the banks, So, DP = 3 metre Angle of depression of the banks on opposite sides of the river are 30 and 45 respectively. So, QPA = 30 and RPB = 45 We need to find width of river i.e. AB Since PD is the height, it is perpendicular to AB PDA = PDB = 90 Lines PQ & AB are parallel, And AP is the transversal PAD = QPA PAD = 30 Similarly, Lines PR & AB are parallel, And BP is the transversal PBD = RPB PBD = 45 Now, AB = AD + BD = 3 3 + 3 = 3( 3 + 1) Width of the river = AB = 3( 3 + 1) metre

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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.