sekant=(1/kosine)
tan=sine/kosine
kotan=kosine/sine
divide both sides bi sekant & yu get (sine/sekant)*(tan+kotan)
=(sine*kosine)*(tan+kotan)
=(sine*kosine)*[(sine/kosine) +(kosine/sine)]
=(sine*kosine)*{ [(sine*sine)/(sine*kosine)] +[(kosine*kosine) / (sine*kosine)]}
=(sine*kosine)/(sine*kosine)*[sine^2+kosine^2]
=1*1....=1