Cos Ф = 3/5
As we know by the trigonometric ratios
Cos Ф = adjacent /hypotenuese
So it means
adjacent /hypotenuese = 3/5
Which means adjacent = 3 and hypotenuese = 5
Now using Pythagorean theorem we can find the opposite side
So opposite ^2 + 3^2 = 5^2
Opposite^2 + 9 = 25
subtract 9 from both sides
Opposite^2 = 16
Opposite = 4
Now tan Ф = opposite/adjacent = 4/3
So
tan Ф = 4/3