What is the sine, cosine and tangent of 30 degrees?
Align the edge of the rule with 30 degrees on the altitude scale in the lower right corner of the back of the astrolabe. The alilade will form a triangle in the right hand shadow box. The triangle (and the box) are ten units wide. The height of the triangle is 6 while the hypotenuse is about 11.5. Using ratios of these numbers, we can calculate sine, cosine and tangent as indicated in the figure below.