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Question Number 81996 by msup trace by abdo last updated on 17/Feb/20

c a l c u l a t e I_{n} = \int \int_{[\frac{1}{n}, n [} e^{- x^{2} - 3 y^{2}} d x d y

a n d f i n d {l i m}_{n \to + \infty} I_{n}

c o n c l u d e t h a t \int_{0}^{\infty} e^{- x^{2}} d x = \frac{\sqrt{π}}{2}