$\require{cancel}\newcommand{\definiteintegral}[4]{\int_{#1}^{#2}\,#3\,d#4} \newcommand{\myequation}[2]{#1\amp =#2} \newcommand{\indefiniteintegral}[2]{\int#1\,d#2} \newcommand{\testingescapedpercent}{ \% } \newcommand{\bvec}{{\mathbf b}} \newcommand{\vvec}{{\mathbf v}} \newcommand{\class}[2][\sim]{\lbrack #2\rbrack_{#1}} \newcommand{\lt}{<} \newcommand{\gt}{>} \newcommand{\amp}{&} \definecolor{fillinmathshade}{gray}{0.9} \newcommand{\fillinmath}[1]{\mathchoice{\colorbox{fillinmathshade}{$\displaystyle \phantom{\,#1\,}$}}{\colorbox{fillinmathshade}{$\textstyle \phantom{\,#1\,}$}}{\colorbox{fillinmathshade}{$\scriptstyle \phantom{\,#1\,}$}}{\colorbox{fillinmathshade}{$\scriptscriptstyle\phantom{\,#1\,}$}}} \newcommand{\sfrac}[2]{{#1}/{#2}} $

Instructions.

View Source for instructions

                                              <instructions xmlns:pi="http://pretextbook.org/2020/pretext/internal">

                                              <p>
Drag some of the points and some of the circles to change them, and watch the remainder react.
                                              </p>

                                              </instructions>

Drag some of the points and some of the circles to change them, and watch the remainder react.