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

**Candy101** · Dec 7th 2012, 03:38 AM

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)

**Plato** · Dec 7th 2012, 04:40 AM

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.

**skeeter** · Dec 7th 2012, 04:44 AM

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 ...

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

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

$\tan(a \pm b) = \frac{\tan(a) \pm \tan(b)}{1 \mp \tan(a)\tan(b)}$

**Candy101** · Dec 9th 2012, 06:43 AM

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?

**skeeter** · Dec 9th 2012, 06:48 AM

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?

here's an idea ... use your calculator to check your work.

**Candy101** · Dec 9th 2012, 07:01 AM

well i just wanted to know if I'm on the right track, and according to my calculator the answer is right, but i just wanted to know if that's the correct way.

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