∫(x-1)^2cosnpixdx
=1/(npi)∫(x-1)^2d(sinnpix)
=1/(npi)(x-1)^2sinnpix+2/(npi)^2∫(x-1)d(cosnpix)
=1/(npi)(x-1)^2sinnpix+2/(npi)^2(x-1)cosnpix-2/(npi)^2∫cosnpixdx
=1/(npi)(x-1)^2sinnpix+2/(npi)^2(x-1)cosnpix-2/(npi)^3sinnpix+C
=(x-1)^2sinnpix/(npi)+2(x-1)cosnpix/(npi)^2-2sinnpix/(npi)^3+C