If the equation a1 + a2cos2x + a3sin2x = 1 is satisfied by every real values of x, then the number of possible values of the triplet (a1,a2,a3)
infinite
a1+a2(2cos2x−1)+a3(1−cos2x) = 1
Or (2a2−a3)cos2x + (a1−a2+a3−1) = 0
This can hold for all x if 2a2−a3 = 0 and a1−a2+a3 - 1 = 0
As there are three variable and two equations, the number of solution is infinite.