Much of the architecture and engineering is based on triangular supports . When an engineer needs to determine the angle by taking into account the length of the cables , the height of the support towers , weight loads and bridge strength , trigonometry helps him calculate the correct angles . It also allows builders to correctly place a curved wall , showing the proper slope of a roof or the correct height of a staircase . In your home , you can use trigonometry to determine the height of a tree or to find square images of a sloping piece of land .