Use trigonometric identities to transform the left side of the equation into the right side (0 <θ < (pi/2)).
1) tanθ cotθ = 1
2) tanθ cotθ = (sinθ)/(cosθ)
3) tanθ cotθ = (sinθ)/(cosθ)²
4) tanθ cotθ = (sinθ)²/(cosθ)