Answer:
B and C
Explanation:
tan (T) = RS/ST = RS/21
⇒ RS = 21tan (T) (choice B)
cos(R) = RS/RT = RS/35
⇒ RS = 35 cos(R) choiice C
tan(R) = 21/RS so that would give RS = 21/tanR not 21 tanR so choice D is out
sin(R) = 21/35 which would give 35 sin(R) = 21 so choice A is out