Both Rhianna and Christopher were correct as they took different reference angles.
Step-by-step explanation:
Step 1:
The value of the tan of a reference angle is calculated using the above formula.
The hypotenuse is the longest side of the triangle is always opposite the right angle of the triangle.
In this triangle, the hypotenuse is the side measuring 5 units.
Step 2:
When the reference angle is A, the opposite side measures 3 units and the adjacent side measures 4 units.
So
When the reference angle is C, the opposite side measures 4 units and the adjacent side measures 3 units.
So
So both Rhianna and Christopher were right as they took different reference angles i.e. A and C.