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Posted by on Wednesday, March 14, 2012 at 11:02am.

Prove that sin3theta=3sintheta-4sin^3theta

  • maths - , Wednesday, March 14, 2012 at 11:08am

    prove sin (3Ø) = 3sin Ø - 4sin^3 Ø

    LS = sin(2Ø + Ø)
    = sin2Ø cosØ + cos2ØsinØ
    = 2sinØcosØcosØ + (1-2sin^2 Ø)sinØ
    = 2sinØ(1-sin^2 Ø) + sinØ - 2sin^3 Ø
    = 2sinØ - 2sin^2 Ø + sinØ - 2sin^3 Ø
    = 3sinØ - 4sin^2 Ø
    = RS

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