Final answer:
The identity/formula used to simplify from step 4 to step 5 is the reciprocal identity for sine, which states that 1/sin(x) = csc(x).
Step-by-step explanation:
The identity/formula used to simplify from step 4 to step 5 is the reciprocal identity for sine:
1/sin(x) = csc(x)
Using this identity, we can rewrite the expression in step 4 as cosecant(x) + cosine(x)/sin(x), which simplifies to cosecant(x) + cotangent(x) in step 5.