# Sine and cos functions

1. Mar 30, 2007

### Ry122

In the function
y=4sin(3X+Pie/4)-2
what determines the period and phase shift?
I know that 4=Amplitude
The answer in the back of the text book says
Period=2pie/3
Phase Shift=-pie/12

2. Mar 30, 2007

### mjsd

standard form:
$$A\sin (kx+\phi)$$
period is given by $$2\pi/k$$

3. Mar 30, 2007

### sutupidmath

Yeah but i think it is better to do it this way, because not always you can immediately determine the period of a function based on that standard form. I think it is better to first know how to come up to that standard form.

so how do we know whether a function is periodic or not?

f(x+T)=f(x), where T is the period.
so after you substitute these values you will be able to find the period of that function, which is the same as ry122 said on his op.

4. Mar 30, 2007

### ChaoticLlama

dessert =/= a mathematical constant, Ry