The area under the curve y=f(x) on [a,b] is square units.
Step-by-step explanation:
The given function is
where a=0 and b=pi/12.
The area under the curve y=f(x) on [a,b] is defined as
Substitute cos (3x)=t, so
Therefore the area under the curve y=f(x) on [a,b] is square units.