The sinusoidal shape is one of the simplest velocity profiles proposed for the boundary layer. Suppose we approximate the velocity distribution as
![1871_e50b638d-66e6-4ebf-9282-9e27a6eebb3c.png](https://secure.tutorsglobe.com/CMSImages/1871_e50b638d-66e6-4ebf-9282-9e27a6eebb3c.png)
Calculate the displacement thickness and the momentum thickness in terms of the local boundary-layer thickness δ.