Sin u = 5/13 and pi/2<u<pi.

Find Sin (u/2); How do you determine the sign (positive or negative) for the value?

Using that information find cos (u/2): I have sqrt(26)/26. Is this positive or negative? How do I know?

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- Jan 11th 2011, 02:39 PMIDontunderstandLocation of half angle
Sin u = 5/13 and pi/2<u<pi.

Find Sin (u/2); How do you determine the sign (positive or negative) for the value?

Using that information find cos (u/2): I have sqrt(26)/26. Is this positive or negative? How do I know? - Jan 11th 2011, 02:47 PMpickslides
- Jan 11th 2011, 02:48 PMPlato
- Jan 11th 2011, 02:49 PMskeeter
- Jan 11th 2011, 03:06 PMsaravananbs
sin u =5/13 and pi/2<u<pi

so find cos u = -12/13 as it is in 2nd quadrant.

use cos u= 2$\displaystyle cos^2 u/2$ -1 to evaluate cos u/2.

you take only positive value as it is in 1st quadrant.

using that you can find sin u/2 also.

since u/2(pi/4<u/2<pi/2 ) is in 1st quadrant

both cos u/2 and sin u/2 are positive. - Jan 11th 2011, 03:30 PMPlato
@saravananbs

Why not learn to post in symbols? You can use LaTeX tags

You do understand that this is not a homework service?

[tex] \sin\left(\frac{u}{2}\right)=\sqrt{\dfrac{1-\cos(u)}{2}} [/tex]

gives $\displaystyle \sin\left(\frac{u}{2}\right)=\sqrt{\dfrac{1-\cos(u)}{2}} $ - Jan 11th 2011, 03:46 PMsaravananbs