Tantalum nitride (TaN) is a chemical compound, a nitride of tantalum. There are multiple phases of compounds, stoichimetrically from Ta2N to Ta3N5, including TaN.
As a thin film TaN find use as a diffusion barrier and insulating layer between copper interconnects in the back end of line of computer chips. Tantalum nitrides are also used in thin film resistors.
y = x tan x
y' = tan x + x*sec^2(x)
y'' = sec^2(x) + d/dx (x*sec^2(x))
= ... + (d/dx(sec^2(x)) + sec^2(x))
= ... + (2secx + sec^2(x))
= 2sec^3 x + sec^4(x)
what did I do wrong?? in book it says y'' = something else.