Trig question on double angle formulas:
Sin theta=3/5, 0

Question

Trig question on double angle formulas: 
Sin theta=3/5, 0<theta<pi/2
Find:
a) sin (2 theta)
b) cos (2 theta)
c) sin theta/2 
d) cos theta/2

fibonaccichick666 · Answer

well, actually 3/5 is a special angle isn't it?

anonymous · Answer

is it?

aum · Answer

|dw:1414112848676:dw|

fibonaccichick666 · Answer

I'm pretty sure, maybe you could draw a picture to think about it

fibonaccichick666 · Answer

or that^

aum · Answer

a)  sin(2t) = 2sin(t)cos(t)
sin(t) = 3/5;  cos(t) = 4/5
sin(2t) = 2 * 3/5 * 4/5 = 24/25

anonymous · Answer

ok I have that part down, and the answers for a and b. I have sin (2 theta)=-24/25 and cos (2 theta)=7/25. I'm not really sure how the formulas work on c and d though the whole thing has me a bit confused

fibonaccichick666 · Answer

How did you get negative?

fibonaccichick666 · Answer

let's look at the first two before we get to C and D

anonymous · Answer

I got a positive but the book told me it was a negative and that x was less than zero but I don't know were that came from, it wasn't a part of the original problem