Malus' law gives the transmitted intensity of polarized light as the square of this function of the polarizer's angle relative to the incoming light. In Compton scattering, the wavelength shift is proportional to 1 minus this function of the scattering angle. The intensity observed from a Lambertian surface is proportional to this function of the angle between the observer and the surface normal. This function's hyperbolic version describes the shape of a freely hanging 
Malus' law gives the transmitted intensity of polarized light as the square of this function of the polarizer's angle relative to the incoming light. In Compton scattering, the wavelength shift is proportional to 1 minus this function of the scattering angle. The intensity observed from a Lambertian surface is proportional to this function of the angle between the observer and the surface normal. This function's hyperbolic version describes the shape of a freely hanging chain supported at both ends and subject to a uniform gravitational force. The dot product of two vectors is given by the product of their magnitudes times this function of the angle between them. For 10 points, identify this trigonometric function whose square plus the square of the sine is always 1.
Malus' law gives the transmitted intensity of polarized light as the square of this function of the polarizer's angle relative to the incoming light.
{cosine}