I'm having trouble with this problem. My professor never showed how to get the answers in the key, so I have no idea how to solve these.

6) Suppose that sinA = 3/5 and tanA<0. Find the following. Clearly explain your reasoning and draw pictures (when appropriate) to help justify your answer.

a) cosA

b) tanA

c) sin(A+pi)

d) sin(-A)

Thanks beforehand for the help.