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Posted by **Public High School Pre Calculus HH** on Sunday, November 15, 2009 at 7:07pm.

sin (- pi/12) csc ( (37 pi)/12

ok now I know this also

sin (- pi /12 ) = - sin ( pi/12)

not really sure how that helps

I don't know were to go from here

( - sin (pi/12) )/(sin ( (25 pi)/12 ) )

- Public High School Pre Calculus HH -
**bobpursley**, Sunday, November 15, 2009 at 7:15pmI thought I answered this.

Remember sin Theta=sin(theta+2PI)

and, remember that sin(-theta)=-sinTheta

so

Sin(-PI/12)=-sin(PI/12)

and lastly, sin(theta)=-sin(theta+PI)

Now, to the task

sin(-PI/12)=-sin(PI/12)= + sin(PI/12+PI)

= sin(13PI/12)=sin(13PI/12+2PI)

= sin(13PI/12+24pi/12)=sin 37PI/12

Now you have

sin(37PI/12)*csc(37pi/12)=1 - READ -
**READ**, Sunday, November 15, 2009 at 7:37pmWhy did you take the negative sign out?

sin(-PI/12)=-sin(PI/12)

I understand this

why are we adding pi to the denomenator

I udner stand that sin (theta) = sin (theta + 2pi)

= + sin(PI/12+PI)

I don't understand that

= sin(13PI/12)

how did we get thirteen ontop?

=sin(13PI/12+2PI)

I understood that

= sin(13PI/12+24pi/12)

so you just rewrote 2pi in therms of a twelth (24pi)/12 makes sense

=sin 37PI/12

ok simplified it

ok so if you can explain the steps i don't understand that would be great thanks!!!! - Public High School Pre Calculus HH -
**bobpursley**, Sunday, November 15, 2009 at 7:47pmsin(PI/12 + PI) is not adding it to the denominator, If I wanted to add it to the denominator..

Sin(PI/(12+PI))

So

Sin(PI/12 + PI)=sin (PI/12 + 12PI/12)=

sin(13PI/12)

go back and reread what I did. - PLEASE READ -
**PLEASE READ**, Sunday, November 15, 2009 at 8:13pmok then everything makes sense you just added pi to make it positive and then everything else makes perfect sense but allows you just to add pi to make it positive?

- Public High School Pre Calculus HH -
**PLEASE READ**, Sunday, November 15, 2009 at 8:15pmwill I do that on my calculator and get the same answer so I guess it's some kind of property of sin...???

- PLEASE READ -
**PLEASE READ**, Sunday, November 15, 2009 at 8:17pmso then I can state this?

for sin (theta)

I can add pi to theta and still get the same answer??? this would appear to be true

does this also hold true for cosine and tangent? - READ READ READ -
**PLEASE READ**, Sunday, November 15, 2009 at 8:21pmSo then

sin - theta + pi = sin theta

cos - theta + pi = cos -theta

ok then I can just simply add pi to it to change it's sign (positive or negative) just like I could with anything without changing it's value????

so we can just simply add pi to theta because it dosen't change its value but it change it's sign which we can do because... - So What Did I do Wrong -
**So What Did I do Wrong**, Sunday, November 15, 2009 at 8:28pmI put this into my calculator and get negative one not positive one

(sin(-pi/12))(sin((25pi)/12))^-1