Maths Core 3 (C3)

Does Sin(theta/2) = sintheta,costheta?

Does Sin(theta/2) = sintheta,costheta?
-If not what does it equal?

What do you mean by your latter sentence? Like what's a nice identity?

I guess you're using the compound angle formula $sin(A + A) = 2sinAcosA$

Notice the angle of the argument on the RHS is half the angle on the argument on the LHS, so $sin(a/2) = 2sin(a/4)cos(a/4)$

or if you want it in terms of another single trig function, start from
$sin^2(x/2) = 1-cos^2(x/2)[br][br]sin(x/2) = \sqrt{1-cos^2(x/2) }$

to get it in terms of tan, try starting from cos^2x + sin^2x =1 and divide through by sin^2x

Thank you, I did workout that it was 2sin(a/4)cos(a/4) but thought it was wrong.Thanks now I know I was correct.
-I discovered these are called Half-angle formulas

Careful, the half angle formula refers to sin a = 2sin(a/2)cos(a/2) and the cos(a/2) one.

but as long as you know the compound angle formula, the names are really unimportant.

or if you want it in terms of another single trig function, start from
$sin^2(x/2) = 1-cos^2(x/2) [br] [br]sin(x/2) = \sqrt{1-cos^2(x/2) }$

Few problems with this that I'm sure you can see?