Diamond Math for the Trig Challenged

Ever wonder how to find the important pavilion and crown main angles from measurements of pavilion depth or table size and crown height? Here's how to get those angles with the help of a couple of buttons on a $16 scientific calculator or the free Windows scientific calculator accessory on your computer. You can use the following steps to check the consistency of angle and percentage results from devices like the Sarin, OGI, or your GIA proportion scope. (Note: You may be surprised at the results!) As always, the accuracy of the calculations depends upon the accuracy of the input measurements. This math assumes a reasonably symmetric diamond with reasonably centered table and culet. First, find the tan and the cos buttons on your scientific calculator. On the calculator shown below, push the shift button and then the tan or cos to obtain the inverse tangent and cosign (tan-1 and cos-

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