概念---金融工程1：外汇的无套利定价模型

Initial Formular（原始公式）:

1+if1+id=SF 1 + i f 1 + i d = S F

S S : Spot exchange rate, e.g S=6.6667 S = 6.6667 for 6.6667 yuan equals to 1 US Dollar( 16.6667≈0.15 1 6.6667 ≈ 0.15 )
F F : Foreign exchange rate
id i d : Domestic interest rate
if i f : Foreign interest rate

Formular transformation:

1S(1+if)F=1+id 1 S ( 1 + i f ) F = 1 + i d

Meaning:
If you have 1 yuan, there is no difference between

get return on domestic deposits with interest rate, 1+id 1 + i d

and

exchange 1 yuan to 1S 1 S $, get return on foreign deposits with 1+if 1 + i f , and then exchange back to 1S(1+if)F 1 S ( 1 + i f ) F yuan.