Crash pulses in automotive collisions often exhibit acceleration shapes somewhere between a sine and a step function and velocity shapes somewhere between a cosine and a linear decay. This is an example of real world behavior that is only somewhat like the familiar sine, cosine, or tangent shapes so commonly used in physical modeling. To adjust the mathematics to the problem, two familiar ordinary differential equations are merged to create a mathematical transition between trigonometric functions and polynomials by introducing one new parameter. The merged ODE produces a new set of “transitional trigonometry” functions that include both sets of familiar shapes and everything in between. For example, the sine function transitions smoothly into a constant or step function. The corresponding cosine function becomes a straight line. When the sine and cosine are plotted against each other the familiar unit circle undergoes a metamorphosis into a square. Integrals of these transitional trigonometric functions transition into a parabola, cubic polynomial, etc. These functions were developed to model a crash pulse in a vehicle collision, a task for which they work remarkably well. Basically, these functions are able to model a structure with force-deflection properties somewhere between a spring with linearly increasing force and a device that produces a constant force. One wonders what other applications in physics may exist besides crashing cars and what other pairs of physical models (represented by ODEs) might be merged together to produce other new and useful transitions.

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