Trigonometry comes up in many aspects of biology. One example is X-ray crystallography, a technique used to determine the three dimensional structure of molecules. X-ray crystallography has been used to determine the atomic structure of thousands of biologically important molecules including vitamins, proteins, and perhaps most famously DNA. X-ray crystallography exploits the fact that when an x-ray is passed through a crystal, it is diffracted according the crystal's atomic structure.

The structure of a crystal can be experimentally determined by Bragg's equation,

nλ = 2dsinθ,

where λ is the wavelength of x-rays, d is the distance between atomic planes, θ is the angle of reflection (in degrees), and n is a positive integer.

Notice that Bragg's equation is a trigonometric function. By the end of this tutorial you should be able to work with this and other trigonometric functions when you encounter them in the classroom or laboratory.

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In the next section we will explore the basics of trigonometric functions.

Basics