What is the formula for rise/fall time of a sine wave?

[Tom McCurdy]

Does anyone remember the formula for the rise/fall time for a sine wave...?

I thought I could calculate it but I did it wrong apparently
t1.
$$V_o sin(2*\pi*f*t)=.1 V_o$$

$$\frac{arcsin(.1)}{2 \pi f}$$

t2.
$$V_o sin(2*\pi*f*t)=.9 V_o$$

$$\frac{arcsin(.9)}{2 \pi f}$$

t2-t1...
but that isn't right

 

[Tom McCurdy]

Ahhh would I just have to change .1 and .9 to
.2 and .8

 

[HallsofIvy]

What, exactly, do you mean by "rise and fall time". The period of the sine function, sin(x), is $2\pi$- that's the "time" for an entire cycle. If, by "rise and fall" time, you mean the time for the function to go up to its highest value and then back to 0, that would be 1/2of that, $\pi$. Or, you might mean the time to rise and the time to fall. Each of those would be $\pi/2$.

Of course, then, I have no idea where you got the "0.1" and "0.9". Or even "0.2" and "0.8"!

 

[f(x)]

how is time in radians ? its just the time period i suppose. And shouldn't the time for rise and fall depend upon wave velocity or wavelength ?