# how to find the exact value of sin,cos and tan of an angle?

• Dec 7th 2012, 04:38 AM
Candy101
how to find the exact value of sin,cos and tan of an angle?
find the exact values of the sine, cosine, and tangent of the angle.

11π/12 = 3π/4 + π/6

can you please explain how to do a question like this step by step.

thank you ( i was not in school when this was done so I'm not sure how or where to start)
• Dec 7th 2012, 05:40 AM
Plato
Re: how to find the exact value of sin,cos and tan of an angle?
Quote:

Originally Posted by Candy101
find the exact values of the sine, cosine, and tangent of the angle.

11π/12 = 3π/4 + π/6

can you please explain how to do a question like this step by step.

thank you ( i was not in school when this was done so I'm not sure how or where to start)

Go to this webpage.
• Dec 7th 2012, 05:44 AM
skeeter
Re: how to find the exact value of sin,cos and tan of an angle?
the two angles on the right side of the equation are unit circle angles ... you should already know the values for sine, cosine, and tangent for each of them.

plug and chug using the sum/difference identities ...

$\sin(a \pm b) = \sin(a)\cos(b) \pm \cos(a)\sin(b)$

$\cos(a \pm b) = \cos(a)\cos(b) \mp \sin(a)\sin(b)$

$\tan(a \pm b) = \frac{\tan(a) \pm \tan(b)}{1 \mp \tan(a)\tan(b)}$
• Dec 9th 2012, 07:43 AM
Candy101
Re: how to find the exact value of sin,cos and tan of an angle?
i try sin

$sin(3pi/4)Cos(pi/6)+cos(3pi/4)sin(Pi/6)$

and i got

√2/2 x √3/2 + -√2/2 x 1/2 = √6 - √2 /4 is this correct?
• Dec 9th 2012, 07:48 AM
skeeter
Re: how to find the exact value of sin,cos and tan of an angle?
Quote:

Originally Posted by Candy101
i try sin

$sin(3pi/4)Cos(pi/6)+cos(3pi/4)sin(Pi/6)$

and i got

√2/2 x √3/2 + -√2/2 x 1/2 = √6 - √2 /4 is this correct?