Question

i.       By first expanding cos(2x + x), show that

   ii.       Hence show that

Solution

     i.
 

We are given that   and we are required to express as;

Therefore;

We have the trigonometric identity;

From this we can write;

Hence;

   ii.
 

We are required to show that;

We have found in (i) that;

Therefore;

Rule for integration of  is:

Rule for integration of  is:

Rule for integration of  is: