Ex 7.3, 7 - Class 12
Last updated at May 29, 2018 by Teachoo
Transcript
Ex 7.3, 7 𝑠𝑖𝑛 4𝑥 sin8𝑥 sin4𝑥sin8𝑥 𝑑𝑥 We know that 2 𝑠𝑖𝑛𝐴 𝑠𝑖𝑛𝐵=− 𝑐𝑜𝑠 𝐴+𝐵+ 𝑐𝑜𝑠 𝐴−𝐵 𝑠𝑖𝑛𝐴 𝑠𝑖𝑛𝐵= 12 − 𝑐𝑜𝑠 𝐴+𝐵+ 𝑐𝑜𝑠 𝐴−𝐵 Replace A by 4𝑥 & B by 8𝑥 sin4𝑥 sin8𝑥= 12 − cos 4𝑥+8𝑥+ cos 4𝑥−8𝑥 sin4𝑥 sin8𝑥= 12 − cos12𝑥+ cos −4𝑥 sin4𝑥 sin8𝑥= 12 − cos12𝑥+ cos4𝑥 sin4𝑥 sin8𝑥= 12 cos4𝑥− cos12𝑥 Integrating both sides sin4𝑥sin8𝑥 𝑑𝑥= 12 cos4𝑥𝑑𝑥− cos12𝑥𝑑𝑥 = 𝟏𝟐 𝐬𝐢𝐧𝟒𝒙𝟒 − 𝒔𝒊𝒏𝟏𝟐𝒙𝟏𝟐+𝑪
Ex 7.3
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About the Author
Davneet Singh
Davneet Singh is a graduate from Indian Institute of Technology, Kanpur. He has been teaching from the past 8 years. He provides courses for Maths and Science at Teachoo. You can check his NCERT Solutions from Class 6 to 12.
