formula

**Dogod11** · December 30th 2009, 06:16 AM

Hello friends, I know, and there is this formula for the sum of sines:

$sin(\alpha) + sin(\beta) = 2sin( \displaystyle\frac{\alpha + \beta}{2} ) cos( \displaystyle\frac{\alpha - \beta}{2} )$

and there is one for the sum of cosines,

I wonder if there is a similar to this:

$tan(\alpha) + tan(\beta)$

greetings

**skeeter** · December 30th 2009, 06:36 AM

Originally Posted by Dogod11

Hello friends, I know, and there is this formula for the sum of sines:

$sin(\alpha) + sin(\beta) = 2sin( \displaystyle\frac{\alpha + \beta}{2} ) cos( \displaystyle\frac{\alpha - \beta}{2} )$

and there is one for the sum of cosines,

I wonder if there is a similar to this:

$tan(\alpha) + tan(\beta)$

greetings

$\tan{\alpha} \pm \tan{\beta} = \frac{\sin(\alpha \pm \beta)}{\cos{\alpha}\cos{\beta}}$

**Dogod11** · December 30th 2009, 07:06 AM

thanks

**mathaddict** · December 30th 2009, 07:28 AM

Originally Posted by Dogod11

Hello friends, I know, and there is this formula for the sum of sines:

$sin(\alpha) + sin(\beta) = 2sin( \displaystyle\frac{\alpha + \beta}{2} ) cos( \displaystyle\frac{\alpha - \beta}{2} )$

and there is one for the sum of cosines,

I wonder if there is a similar to this:

$tan(\alpha) + tan(\beta)$

greetings

HI

$<br /> \frac{\sin \alpha\cos \beta \pm \cos \alpha \sin \beta}{\cos \alpha\cos \beta}=\frac{\sin (\alpha\pm \beta)}{\cos \alpha\cos \beta}<br />$

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