What is the formula for cos3a.and also tell about the method to get it
Mohit , 9 Years ago
Grade 9
Trigonometry> What is the formula for cos3a.and also te...
1 Answers
Nikhil Upadhyay
Last Activity: 9 Years ago
cos3a=4cos3a-3cosa.you can get it by writing it in the form cos(a+b) as cos(2a+a)
=cos2a*cosa-sin2a*sina
=(2cos2a-1)cosa-2sinacosasina
=(2cos2a-1)cosa-2cosa(1-sin2a)
=2cos3a-cosa-2cosa+2cos3a
=4cos3a-3cosa.PLZ approve
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