The geometric average in time of geometric Brownian motion is lognormal distributed. These equations express the two parameters of the lognormal distribution as a function of the continuosly sampled geometric average. Averaging starts at t and stops at T. An application is the Vorst model for Asian options. In this model the arithmetic average of the Asian options is approximated with a geometric average.

List of symbols

Y	Yield of the underlying
	Effective yield of the geometric average
	Volatility
	Effective volatility of the geometric average
t	Start of the averaging period
T	End of the averaging period

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