Given that a = -3/4 and a is in the interval $$p,3p/2$$, let's find sin$a$, tan$a$, and cot$a$.

First, let's find the reference angle for 'a' within the given interval $$p,3p/2$$.

a = -3/4
To find the reference angle, we add 2π to a in order to get it in the desired interval:

a = -3/4 + 2π
a = 5π/4

Now, we will find sin$a$, tan$a$, and cot$a$.

sin$a$ = sin$5\pi /4$ sin$5\pi /4$ = -√2 / 2

tan$a$ = tan$5\pi /4$ tan$5\pi /4$ = sin$5\pi /4$ / cos$5\pi /4$ tan$5\pi /4$ = -√2 / 2 / $-1/\surd 2$ tan$5\pi /4$ = √2

cot$a$ = 1 / tan$5\pi /4$ cot$5\pi /4$ = 1 / √2

Therefore, sin$a$ = -√2 / 2, tan$a$ = √2, and cot$a$ = 1 / √2.