(b) 0 < tan1(Y/X) < and Y > 0. (Consider various cases depending on the relative sizes of a, b, and c.) (Oxford 1981M)

(b) 0 < tan−1(Y/X) < α and Y > 0.

(Consider various cases depending on the relative sizes of

a, b, and c.) (Oxford 1981M)

13. The independent random variables X and Y are both exponentially distributed with parameter

λ, that is, each has density function f (t ) =

(

λe−λt if t > 0, 0 otherwise.