Here's a graph for the first one :
https://www.desmos.com/calculator/eijmu9tzm9
csc A = r / y
r = sqrt [ (-4)^2 + (-6)^2 ] = sqrt [ 16 + 36] = sqrt [52] = sqrt [4 * 13] = sqrt (4) * sqrt (13) = 2sqrt (13)
So
csc A = 2 sqrt (13) / -6 = -sqrt (13) / 3
