Math Help - identities and equations?

1. identities and equations?

hi, I know that you need to sub in a trig identity to the equation... but I don't know which one or what to do... I'm so confused.

sin(2theta) + 4cos(theta) = 0

2. Originally Posted by [nuthing]
hi, I know that you need to sub in a trig identity to the equation... but I don't know which one or what to do... I'm so confused.

sin(2theta) + 4cos(theta) = 0
use the double angle identity, $\sin(2t) = 2\sin{t}\cos{t}$, factor and solve.

3. Originally Posted by skeeter
use the double angle identity, $\sin(2t) = 2\sin{t}\cos{t}$, factor and solve.
yeah, but how?

4. Originally Posted by [nuthing]
yeah, but how?
Well can you factor $2xy-4y~?$

5. Originally Posted by [nuthing]
yeah, but how?
1. Use the double angle formula
2. Factor
3. Solve

1. sin(2t) + 4cos(t) = 0 becomes
2sin(t)cos(t) + 4cos(t) = 0
2. Take out the greatest common factor
3. Set each factor equal to zero, using the "zero product property" (field)