If cos θ+cos 2θ+ cos 3θ=0 then θ=

If tan (π/2 sin θ) = cot (π/2 cos θ) then sin (θ+ π/4) =

If tan x+ tan 4x+tan 7x=tan x tan 4x tan 7x, then x=

If cos 2θ+cos 8θ= cos 5θ then θ=

If 2-cos³ θ=3 sin θ cos θ then θ=

The solution of sin 2θ+cos 2θ+sin θ+ cos θ+1=0 in the first quadrant is

The solution set of sec θ=2cos θ is

If tan² θ=3 cosec² θ-1 then θ=

The domain of Cos^-1 (4x-9) is

If tan (cot x) = cot (tan x), then sin 2x=