CBSE Class 11-science Answered
Q10
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Asked by omved0304 | 07 Aug, 2020, 11:24: AM
To prove that cot 4x (sin 5x + sin 3x) = cot x (sin 5x - sin 3x)
![cot 4 straight x space left parenthesis sin 5 straight x space plus space sin 3 straight x right parenthesis equals fraction numerator cos 4 straight x over denominator sin 4 straight x end fraction space left parenthesis sin 5 straight x space plus space sin 3 straight x right parenthesis
equals fraction numerator cos 4 straight x over denominator sin 4 straight x end fraction open square brackets 2 sin open parentheses fraction numerator 5 straight x plus 3 straight x over denominator 2 end fraction close parentheses cos open parentheses fraction numerator 5 straight x minus 3 straight x over denominator 2 end fraction close parentheses close square brackets equals fraction numerator cos 4 straight x over denominator sin 4 straight x end fraction open square brackets 2 sin 4 straight x space cos space straight x close square brackets equals 2 space cos 4 straight x space cosx
cotx space open parentheses sin 5 straight x space minus space sin 3 straight x close parentheses equals cosx over sinx open parentheses sin 5 straight x minus sin 3 straight x close parentheses
equals fraction numerator cos 4 straight x over denominator sin 4 straight x end fraction open square brackets 2 cos open parentheses fraction numerator 5 straight x plus 3 straight x over denominator 2 end fraction close parentheses sin open parentheses fraction numerator 5 straight x minus 3 straight x over denominator 2 end fraction close parentheses close square brackets equals cosx over sinx open square brackets 2 cos 4 straight x space sinx close square brackets equals 2 space cosx space cos 4 straight x
Hence comma space cot 4 straight x space left parenthesis sin 5 straight x space plus space sin 3 straight x right parenthesis equals cotx space open parentheses sin 5 straight x space minus space sin 3 straight x close parentheses](https://images.topperlearning.com/topper/tinymce/cache/9f92f07510b7cb0f39f038d822cf0c45.png)
Answered by Renu Varma | 11 Aug, 2020, 12:08: PM
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