Rita i proving that the following trigonometric identity i true: co(−θ)in(−θ)=−1tanθ Which tep would be the firt line of her proof? Repone co(−θ)⋅tanθ=in(−θ) coine of begin argument negative theta end argument time tangent of theta equal ine of begin argument negative theta end argument coθ−inθ=−1tanθ fraction numerator coine of theta end numerator over denominator negative ine of theta end fraction equal negative fraction numerator 1 over denominator tangent of theta end fraction coθinθ=−1tanθ fraction numerator coine of theta end numerator over denominator ine of theta end fraction equal negative fraction numerator 1 over denominator tangent of theta end fraction co(−θ)inθ=−1tanθ