Question

if cos3x=4cos^3 30degree-3cos3zero degree find x​

Answer 1

Answer:

orange\boxed{QUESTION}

If x = 30°

verify that , cos 3 x = 4 cos³ x - 3 cos x.

\blue\boxed{knowledge\:required}

value of cos 30° = √3 / 2

value of cos 90° = 0

\green\boxed{SOLUTION}

substituting x = 30° in LHS

we will get,

LHS = cos 3 (30°) = cos 90° = 0

now, substituting x = 30° in RHS

RHS = 4 cos³*30° - 3 cos 30°

RHS = 4 (√3/2)³ - 3 ( √3 / 2 )

RHS = 4 ( 3√3 / 8 ) - (3√3 / 2)

RHS = ( 3√3/2) - (3√3/2)

RHS = 0

\begin{gathered}\yellow{LHS=RHS}\\\\hence proved.\end{gathered}

\yellowLHS=RHS

henceproved.

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Answer 2

Answer:

hope it helps

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