Helicopter is a pilates exercise that deeply works on the abs, it strengthens them, but it helps also slim hips and thighs.
You are on the back, the arms are along your body sides. Spread the legs like a scissor with the right leg forward and the left leg a little raised from the floor. Make two small and fast movements by trying to bringing away the legs from each other and then by bringing them back to the initial pose. Repeat by changing the leg.
Stay on the back, legs straight. Raise the right leg from the floor and bring it to the left. Make a big rotation outwards, go on for 8 times. The shoulders should stay both on the mat. Repeat with the other leg.
You are on your back. Bring the legs perpendicular to the floor, open the legs like a scissor and rotate both the legs outwards, then return to the initial pose. Repeat for 8 times, then change the leg.