Which of the following sine functions has a period of 4 π ?

Can someone me and do the problem plz so i can understand it more better

If t17 = 3 (t5) in an arithmetic progression, find t1 in terms of d.

The perimeter of ? cde is 55 cm. a rhombus dmfn is inscribed in this triangle so that vertices m, f, and n lie on the sides cd , ce , and de respectively. find cd and de if cf=8 cm and ef=12 cm. the answer is not cd=20 and de=15. i have tried that one, it does not work.