sin(3x) = 3cos^{2}x.sin(x)-sin^{3}x.
Please give me proof for above formula.
prasanth battula , 13 Years ago
Grade 12
Trigonometry> sin-3x...
3 Answers
Raghuvaran varan Chandragiri
sin(2x+x)=sin2x.cosx+cos2x.sinx
=2sinxcosx.cosx+(-2sin^2x)sinx
=2sinxcos^2+sinx-2sin^3x
=sinx(2cos^2x+1)-2sin^3x
=sinx(2-2sin^2x+1)-2sin^3x
=2sinx-2sin^3x+sinx-2sin^3x
= 3sinx-4sin^3x
badapalli Kurmarao
sin(2x+x)=sin2x.cosx+cos2x.sinx
=2sinxcosx.cosx+(-2sin^2x)sinx
=2sinxcos^2+sinx-2sin^3x
=sinx(2cos^2x+1)-2sin^3x
=sinx(2-2sin^2x+1)-2sin^3x
=2sinx-2sin^3x+sinx-2sin^3x
= 3sinx-4sin^3x
prasanth battula
thank you,you missed putting 1 in the second step in your answer
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