R = 1
C = 0.000001

T = function(x){
 1/sqrt(1+4*(pi*x*R*C)^2)
}



xcost = c(1,1000000)
cut = 1/sqrt(2)
ycost = c(cut,cut)

fcut = 1/(2*pi*R*C)
fcost = c(fcut,fcut)
tcost = c(0,1)

curve(T, from=1, to=1000000, , xlab="f (Hz)", ylab="T")
points(xcost,ycost, type = "l", col = 2)
points(fcost,tcost, type = "l", col = 3)


TdB = function(x){
 10*log(1/sqrt(1+4*(pi*x*R*C)^2), base = 10)
}


xcost = c(1,1000000)
cut = 10*log(1/sqrt(2), base = 10)
ycost = c(cut,cut)

fcut = 1/(2*pi*R*C)
fcost = c(fcut,fcut)
tcost = c(-10,0)


curve(TdB, from=1, to=1000000, , xlab="f (Hz)", ylab="T (dB)")


curve(TdB, from=1, to=1000000, , xlab="f (Hz)", ylab="T (dB)", log = "x")
points(xcost,ycost, type = "l", col = 2)
points(fcost,tcost, type = "l", col = 3)