12th maths exercise 2.8 question 4/if 2cos=x+1/x and 2cos=y+1/y show that x/y+y/x=2cos....

if 2cos=x+1/x and 2cos=y+1/y show that x/y+y/x=2cos, xy-1/xy=2isin,x^m/y^m-y^m/x^m=2isin,x^my^n+1/x^my^n=2cos