Rita is proving that the following trigonometric identity is true: cos(−θ)sin(−θ)=−1tanθ

Which step would be the first line of her proof?

cosθsinθ=−1tanθ
cosθ−sinθ=−1tanθ
cos(−θ)sinθ=−1tanθ
cos(−θ)⋅tanθ=sin(−θ)

PLEASE ANSWER WILL MARK BRAINLIEST