一道英文的数学题…… 没看懂

一道英文的数学题…… 没看懂A child swings back and forth,reaching a maximum angle of 32° with the vertical.The swing is 3.4 m long and 0.75 m from the ground when at rest.What maximum height above the ground does the child reach.“The swing is 3.4 m long and 0.75 m from the ground when at rest.”