求Coupon rate = Yield to maturity, when Sale price = Face Value
let:
Coupon Rate = I,
Yield to maturity = R,
Face Value = P,
so Sale Price = P,
who can help me to prove that R = I, when sale price = face value
p=(p*i)/[(1+r)^1]+(p*i)/[(1+r)^2]+(p*i)/[(1+r)^3]+(p*i)/[(1+r)^4]...............+(p*i)/[(1+r)^n]+P/[(1+r)^n]