13. Cos^-1(- square root of 3/2) arccos() = . 14. Sin^-1 (-squareroot of 2/2) arcsin( ) = . 15. Arctan (-squareroot of 3/3) arctan(( ) = . 16. tan (Cos^-1 1/2) tan(arccos( ) = tan( ) = . 17. cos (sin^-1 (-3/5)) . 18. cos (Arctan (-1)) cos(arctan(-1)) = cos( ) = . 19. tan (sin^-1 12/13) . 20. sin (Arctan -squareroot 3/3) sin(arctan( ) = sin( ) = . 21. Cos^-1 (tan 3pi/4) arccos(tan( ) = arccos(-1) = . 22. Sin^-1 (cos(pi/ 3)) arcsin(cos ) = arcsin( ) = .