Stuck on this math question

Answer:
SinA = √5/3
CosB = √5/3
Step-by-step explanation:
First let us find the value of a. This is illustrated below:
a^2 = 6^2 — 4^2
a^2 = 36 — 16
a^2 = 20
Take the square root of both side
a = √20 = √(4 x 5) = √4 x √5
a = 2√5
From the diagram,
For sinA
Opp = 2√5
Hypo = 6
Adj = 4
SinA = opp /Hypo
SinA = 2√5/6
SinA = √5/3
For CosB
Opp = 4
Hypo = 6
Adj = 2√5
CosB = Adj /Hypo
CosB = 2√5/6
CosB = √5/3