how would i calculate the approximate frequency of the sinewave? see parameters below

[Hamzah712]

so suppose i have a single-pole (first-order) low-pass RC filter that gives me a unity gain upto the corner frequency of 1536Hz and i apply a 12V amplitude sinewave to the input of the filter and i am getting a sinewave with the amplitude of 4.1V from the output of the filter

 

[Lucien Nunes]

You have the amplitudes so you can calculate the attenuation. You need an equation for the gain of a first order filter in terms of signal frequency and corner frequency, then rearrange it for signal frequency...

But see my comment in your latest thread!