sin(3x)cos(6x)-cos(3x)sin(6x)=-0.9

I solve like this

sin(3x)cos(6x)-cos(3x)sin(6x)=-0.9

sin(3x-6x)=-0.9

sin(-3x)=-0.9

-sin(3x)=-0.9

sin(3x)=0.9

but the answer are 0.373+2π/3k and 0.6742π/3k

π is pi.

help please? am I doing the right way?

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- December 4th 2012, 05:35 AMedmundyongTrigonometric - Addition and subtraction Identities
sin(3x)cos(6x)-cos(3x)sin(6x)=-0.9

I solve like this

sin(3x)cos(6x)-cos(3x)sin(6x)=-0.9

sin(3x-6x)=-0.9

sin(-3x)=-0.9

-sin(3x)=-0.9

sin(3x)=0.9

but the answer are 0.373+2π/3k and 0.6742π/3k

π is pi.

help please? am I doing the right way? - December 4th 2012, 05:40 AMProve ItRe: Trigonometric - Addition and subtraction Identities
What you've done so far is fine, now you just have to evaluate the values of x...

- December 4th 2012, 06:09 AMedmundyongRe: Trigonometric - Addition and subtraction Identities
got it! stupid me! I forget to change my answer to radian mode.

thank you