ヤコビ行列計算機
ステップバイステップでヤコビ行列を計算する
この計算機は、関数の組のヤコビ行列と(可能であれば)ヤコビ行列式を、手順付きで求めます。
入力内容
$$$\left\{x = r \cos{\left(\tanh{\left(\eta \right)} \right)}, y = r \sin{\left(\tanh{\left(\eta \right)} \right)}\right\}$$$ のヤコビ行列を計算してください。
解答
ヤコビ行列は次のように定義されます: $$$J{\left(x,y \right)}\left(\eta, r\right) = \left[\begin{array}{cc}\frac{\partial x}{\partial \eta} & \frac{\partial x}{\partial r}\\\frac{\partial y}{\partial \eta} & \frac{\partial y}{\partial r}\end{array}\right].$$$
この場合、$$$J{\left(x,y \right)}\left(\eta, r\right) = \left[\begin{array}{cc}\frac{\partial}{\partial \eta} \left(r \cos{\left(\tanh{\left(\eta \right)} \right)}\right) & \frac{\partial}{\partial r} \left(r \cos{\left(\tanh{\left(\eta \right)} \right)}\right)\\\frac{\partial}{\partial \eta} \left(r \sin{\left(\tanh{\left(\eta \right)} \right)}\right) & \frac{\partial}{\partial r} \left(r \sin{\left(\tanh{\left(\eta \right)} \right)}\right)\end{array}\right]$$$ となります。
導関数を求めよ(手順は derivative calculator を参照):$$$J{\left(x,y \right)}\left(\eta, r\right) = \left[\begin{array}{cc}- r \sin{\left(\tanh{\left(\eta \right)} \right)} \operatorname{sech}^{2}{\left(\eta \right)} & \cos{\left(\tanh{\left(\eta \right)} \right)}\\r \cos{\left(\tanh{\left(\eta \right)} \right)} \operatorname{sech}^{2}{\left(\eta \right)} & \sin{\left(\tanh{\left(\eta \right)} \right)}\end{array}\right]$$$。
ヤコビ行列式はヤコビ行列の行列式である: $$$\left|\begin{array}{cc}- r \sin{\left(\tanh{\left(\eta \right)} \right)} \operatorname{sech}^{2}{\left(\eta \right)} & \cos{\left(\tanh{\left(\eta \right)} \right)}\\r \cos{\left(\tanh{\left(\eta \right)} \right)} \operatorname{sech}^{2}{\left(\eta \right)} & \sin{\left(\tanh{\left(\eta \right)} \right)}\end{array}\right| = - r \operatorname{sech}^{2}{\left(\eta \right)}$$$(手順は行列式計算機を参照)。
解答
ヤコビ行列は$$$\left[\begin{array}{cc}- r \sin{\left(\tanh{\left(\eta \right)} \right)} \operatorname{sech}^{2}{\left(\eta \right)} & \cos{\left(\tanh{\left(\eta \right)} \right)}\\r \cos{\left(\tanh{\left(\eta \right)} \right)} \operatorname{sech}^{2}{\left(\eta \right)} & \sin{\left(\tanh{\left(\eta \right)} \right)}\end{array}\right]$$$Aです。
ヤコビ行列式は$$$- r \operatorname{sech}^{2}{\left(\eta \right)}$$$Aです。