Memory slippage

Show: (x sin θ + y cos θ)² + (x cos θ – y sin θ)² = x² + y²

If only I’d have known 4 years ago that I was going to be teaching this stuff today…

And the good times continue at FBCS…

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One Response to Memory slippage

  1. Marlin says:

    (x sin Q + y cos Q)² + (x cos Q – y sinQ)²
    X2 sin2Q + 2xy sinQcosQ +y2cos2Q +x2cos2Q – 2xy cosQsinQ +y2sin2Q
    X2(sin2Q+ cos2Q)+ y2(sin2Q+ cos2Q)
    X2+ y2

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