You know how Soh Cah Toa applies to right triangles; you can assign the adjacent side = 4 and hypotenuse = 7
CosФ = (adjacent) / (hypotenuse)
Then with the Pythagorean theorem
4² + b² = 7²
16 + b² = 49
b² = 49 - 16
b² = 33
b = √(33)
So "b" is the opposite side.
SinФ = (opposite) / (hypotenuse) = √(33)/7
TanФ = (opposite) / (adjacent) = √(33)/4