I'm working with FRDM K64F, I need to use trigonometric functions but i don't know how I can enable the floating point unit for usetrigonometric functions.
Just add one information here:
From hardware perspective, floating point setting is in devices/mk64f12/MK64F12.h
#define __FPU_PRESENT 1 /**< Defines if an FPU is present or not */
From IDE perspective, there is a Floating point configuration setting in MCUXpresso Project properties.
If you are using one of the MCUXpresso SDK projects for any M4F (e.g. K64F), then the FPU is already enabled.