Prove that sec^2x+cosec^2x>=4

Sec^2x+Cosec^2x= 1/cos^2x + 1/sin^2x = (cos^2x+sin^2x) / cos^2x sin^2x
= 1 / ​cos^2x sin^2x = 4 / sin^2 2x

4 / sin^2 2x >=4