Question

1-cos3A/1-cosA=(1+2cosA)^2​

Answer 1

Step-by-step explanation:

1-cos3A/1-cosA

1-cos3A/1-cosA=1-4cos³A+3cosA/1-cosA

1-cos3A/1-cosA=1-4cos³A+3cosA/1-cosA=4cos³A-3cosA-1/cosA-1

=4cos²A(cosA-1)+4cos²A-3cosA-1/cosA-1

=[4cos²A(cosA-1)+4cosA(cosA-1)+(cosA-1)] / (cosA-1)

=(cosA-1)(4cos²A+4cosA+1)/cosA-1

=4cos²A+4cosA+1

=(2cosA)² +2×2cosA +1²

= (2cosA+1)²

=(1+2cosA)²

Answer 2

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