Given that
tanθ - cotθ = a ....(i)
and sinθ + cosθ .....(2)
Now,
Trick: Obviously the value of expression (b2 - 1)2 (a2 + 4) is independent of θ , therefore put any suitable value of θ. Let θ = 45° . We get a = 0, b = 2 so that [√2]2 - 1]2(02 + 4) = 4 .