cos2AcosA/2-cos3Acos9A/2=sin5Asin5A/2

Asked by Anil | 6th Jun, 2017, 07:21: PM

Expert Answer:

begin mathsize 16px style cos 2 Acos straight A over 2 minus cos 3 Acos fraction numerator 9 straight A over denominator 2 end fraction
equals 1 half open parentheses 2 cos 2 Acos straight A over 2 minus 2 cos 3 Acos fraction numerator 9 straight A over denominator 2 end fraction close parentheses
Using space 2 cosAcosB equals cos open parentheses straight A plus straight B close parentheses minus cos open parentheses straight A minus straight B close parentheses
equals 1 half open parentheses 2 cos 2 Acos straight A over 2 minus 2 cos 3 Acos fraction numerator 9 straight A over denominator 2 end fraction close parentheses
equals 1 half open square brackets cos fraction numerator 5 straight A over denominator 2 end fraction plus cos straight A over 2 minus open parentheses cos fraction numerator 15 straight A over denominator 2 end fraction plus cos fraction numerator 3 straight A over denominator 2 end fraction close parentheses close square brackets
equals 1 half open square brackets cos fraction numerator 5 straight A over denominator 2 end fraction minus cos fraction numerator 15 straight A over denominator 2 end fraction close square brackets
equals 1 half cross times 2 sin 5 Asin fraction numerator 5 straight A over denominator 2 end fraction end style

Answered by Sneha shidid | 7th Jun, 2017, 08:42: AM