1. The problem statement, all variables and given/known data I was solving a problem involving sine and cosine ratios. If I come to know the maximum possible value of (sin x+cos x), x belongs to [0,2*pi]. my problm would be solved. 2. Relevant equations 3. The attempt at a solution I think x ill be in 1st quadrant as both sin and cos are +ve. If I am not wrong x=45???? but how do i mathematically prove this?