Home/Differential Calculus/Tangent and normal lines/Formula4.2. Tangent and normal linesFormulaIn 4.2. Tangent and normal linesFormulaCopy LaTeXmtan=f′(a)m_{\mathrm{tan}}=f'(a)mtan=f′(a)TagsDifferential calculusDerivativeTangent and normal linesDerivative formulaDetailSlope of the tangent.VariablesaaaPoint or real constantfffFunctionf′f'f′Derivative of fffFound an error? Contact us.Related formulasRelatedFormulay−f(a)=−1f′(a)(x−a),f′(a)≠0y-f(a)=-\frac{1}{f'(a)}(x-a),\qquad f'(a)\neq0y−f(a)=−f′(a)1(x−a),f′(a)=0Open formulaOpen in sectionRelatedFormulav(t)=s′(t)v(t)=s'(t)v(t)=s′(t)Open formulaOpen in sectionRelatedFormulay−f(a)=f′(a)(x−a)y-f(a)=f'(a)(x-a)y−f(a)=f′(a)(x−a)Open formulaOpen in section