trig functions

[arginine1]

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My last math course was calculus.. 3 years ago. Too bad all this time I wasn't using trig functions on daily basis.. just for entertainmnet purposes😛

Anyways... there was this problem stating that sin(2x) = 2sin(x)cos(x)

I'm not familiar with this identity or anything similar to it.

Can anyone clarify this for me?🙁

 

[Shingo123]

My last math course was calculus.. 3 years ago. Too bad all this time I wasn't using trig functions on daily basis.. just for entertainmnet purposes😛

Anyways... there was this problem stating that sin(2x) = 2sin(x)cos(x)

I'm not familiar with this identity or anything similar to it.

Can anyone clarify this for me?🙁

That is called the double angle identity.

See here: http://www.sosmath.com/trig/douangl/douangl.html

 

[arginine1]

thanks..

that link just made me wanna cry.... there is no way I can get familiar with all these functions

 

[Streetwolf]

thanks..

that link just made me wanna cry.... there is no way I can get familiar with all these functions

You don't need most of the ones on that page.

Know sin(2x) and cos(2x).

My teacher always did...

cos(x + y) = (cosine of the first, times cosine of the second), minus (sine of the first, times sine of the second).

In other words cos(x+y) = cos(x)cos👍 - sin(x)sin👍.

sin(x + y) = (sine of the first, times cosine of the second), plus (sine of the second, times cosine of the first).

In other words sin(x+y) = sin(x)cos👍 + sin👍cos(x).

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To get the double angle formulas, let x = y.

Subtraction (eg sin(x-y)) would swap the plus/minus sign.