Question

i. Show that the equation

Can be written in the form

ii. Hence solve the equation to

For .

Solution

i.

We are given;

We apply following two addition formulae on both sides of given equation.

Therefore;

Since;

ii.

We are required to solve following equation doe .

We have found in (i) that it can be written as;

Let , then;

Now we have two options.

Since , therefore;

Using calculator we can find that

We utilize the periodicity/symmetry property of to find other solutions (roots) of :

Therefore;

For ;

For ;

Only following solutions (roots) are within the given interval ;