Quandaries
and Queries 

name : kris i am a student secondary 1012 or 11th how to solve the equation please solve it 

Hi Kris, Use the double angle expression for the cosine to get
Then replace cos^{2}(x) by 1  sin^{2}(x) to get
which simplifies to
If you let y = sin(x) then this equation is a quadratic in y which you can solve. This will give you two values for y which then gives you two equations
to solve for x. Penny 

