Hey Riley, remember the sum rule for derivatives? {{CMD_7}} You know I do. {{CMD_8}} What do you think that the ``product rule'' will be? {{CMD_9}} Let's give this a spin: {{MATH_10}} {{CMD_11}} Hmmm, let's give this theory an acid test. Let's try {{MATH_12}} Now {{ENV_13}} {{CMD_14}} On the other hand, {{ENV_15}} {{CMD_16}} And so, {{MATH_17}} {{CMD_18}} Wow. Hmmm. It looks like our guess was incorrect. {{CMD_19}} I've got a feeling that the so-called ``product rule'' might be a bit tricky. {{CMD_20}}