Finding a Tangent Plane to a Surface – Multivariable Calculus Example

Finding a Tangent Plane to a Surface – Multivariable Calculus Example

This page is nothing more than a free preview of The Ultimate Crash Course for STEM Majors. This multivariable calculus example demonstrates how to find the equation of a tangent plane to a surface using an implicit function, partial derivatives, and the gradient vector.

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[13] Tangent Planes

Find an equation of the tangent plane to the given surface at the specified point.

\[ z=x\sin(x+y), \qquad P(-1,1,0) \]

The easiest formula to use is

\[ f(x,y,z)=0, \qquad P_0=P(x_0,y_0,z_0) \]
\[ f_x(P_0)\Delta x+f_y(P_0)\Delta y+f_z(P_0)\Delta z=0. \]
\[ z=x\sin(x+y) \Rightarrow f(x,y,z)=z-x\sin(x+y)=0 \]
\[ \nabla f = \left\langle -x\cos(x+y)-\sin(x+y), -x\cos(x+y), 1 \right\rangle \]
\[ \nabla f(-1,1,0) = \left\langle -(-1)\cos(-1+1)-\sin(-1+1), -(-1)\cos(-1+1), 1 \right\rangle \]
\[ = \langle 1,1,1\rangle. \]
\[ f_x(x_0,y_0,z_0)(x-x_0) + f_y(x_0,y_0,z_0)(y-y_0) + f_z(x_0,y_0,z_0)(z-z_0) = 0 \]
\[ (1)(x-(-1))+(1)(y-1)+(1)(z-0)=0 \]
\[ x+1+y-1+z=0 \]
\[ x+y+z=0. \]
\[ z=x\sin(x+y), \qquad P(-1,1,0) \]
\[ x+y+z=0 \]

The original lesson includes a 3D visualization of the surface \(z=x\sin(x+y)\) and its tangent plane at \(P(-1,1,0)\).

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This lesson is nothing more than a free preview of The Ultimate Crash Course for STEM Majors. Continue with the complete series for worked examples involving tangent planes, multivariable calculus, gradients, partial derivatives, vector calculus, differential equations, mathematics, physics, engineering, and other STEM subjects.

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