Find the area under the curve given by y=coax from x=0 to x=pi/4 above the x-axis.

Draw a graph with an approximate rectangle (ie cut).
Calculate the area with an integral.

Area = ∫ cosx dx from 0 to π/4

= [sinx] from 0 to π/4
= sinπ/4 - sin0
= √2/2-0
= √2/2