Which of the following gives the least value of A

(a)cos⁡2A=sin⁡3A=cos⁡(π/2−3A)⇒5A=π/2=A=π/10  (b) â‡’10A=π/2⇒A=π/20(c)⇒A=π/8,(d)⇒A=π/6Least value of A is Ï€/20 given by (b).