In one sentence, describe what the following article is about:

Draw your table to have 6 rows and 6 columns. In the first column, write down the trigonometric ratios (sine, cosine, tangent, cosecant, secant, and cotangent). In the first column, write down the angles commonly used in trigonometry (0, 30, 45, 60, 90). Leave the other entries in the table blank. Sine, cosine, and tangent are the more commonly used trigonometric ratios, although you should also learn cosecant, secant, and cotangent to have an in-depth knowledge of the trigonometric table. Use the expression x/2 to fill in the blank entries in this column. The x value should be that of the angle listed on the left-hand side of the table. Use this formula to calculate the sine values for 0, 30, 45, 60, and 90 and write those values in your table. For example, for the first entry in the sine column (sin 0), set x to equal 0 and plug it into the expression x/2. This will give you 0/2, which can be simplified to 0/2 and then finally to 0. Plugging the angles into the expression x/2 in this way, the remaining entries in the sine column are 1/2 (which can be simplified to , since the square root of 1 is 1), 2/2 (which can be simplified to 1/2, since 2/2 is also equal to (1 x 2)/(2 x 2) and in this fraction, the "2" in the numerator and a "2" in the denominator cancel each other out, leaving 1/2), 3/2, and 4/2 (which can be simplified to 1, since the square root of 4 is 2 and 2/2 = 1). Once the sine column is filled, it'll be a lot easier to fill in the remaining columns. Mathematically speaking, sin x = cos (90-x) for any x value. Thus, to fill in the cosine column, simply take the entries in the sine column and place them in reverse order in the cosine column. Fill in the cosine column such that the value for the sine of 90 is also used as the value for the cosine of 0, the value for the sine of 60 is used as the value for the cosine of 30, and so on. For example, since 1 is the value placed in the final entry in the sine column (sine of 90), this value will be placed in the first entry for the cosine column (cosine of 0). Once filled, the values in the cosine column should be 1, 3/2, 1/2, , and 0. Simply speaking, tangent = sine/cosine. Thus, for every angle, take its sine value and divide it by its cosine value to calculate the corresponding tangent value. To take 30 as an example: tan 30 = sin 30 / cos 30 = (1/2) / (3/2) = 1/3. The entries of your tangent column should be 0, 1/3, 1, 3, and undefined for 90. The tangent of 90 is undefined because sin 90 / cos 90 = 1/0 and division by 0 is always undefined. Starting from the bottom row of the sine column, take the sine values you've already calculated and place them in reverse order in the cosecant column. This works because the cosecant of an angle is equal to the inverse of the sine of that angle. For instance, use the sine of 90 to fill in the entry for the cosecant of 0, the sine of 60 for the cosecant of 30, and so on. Starting from the cosine of 90, enter the values from the cosine column in the secant column, such that value for the cosine of 90 is used as the value for the secant of 0, the value for the cosine of 60 is used as the value for the secant of , and so on. This is mathematically valid because the inverse of the cosine of an angle is equal to that angle's secant. Take the value for the tangent of 90 and place it in the entry space for the cotangent of 0 in your cotangent column. Do the same for the tangent of 60 and the cotangent of 30, the tangent of 45 and the cotangent of 45, and so on, until you've filled in the cotangent column by inverting the order of entries in the tangent column. This works because the cotangent of an angle is equal to the inversion of the tangent of an angle. You can also find the cotangent of an angle by dividing its cosine by its sine.

Summary:
Create a blank trigonometry table. Fill in the values for the sine column. Place the sine column entries in the cosine column in reverse order. Divide your sine values by the cosine values to fill the tangent column. Reverse the entries in the sine column to find the cosecant of an angle. Place the entries from the cosine column in reverse order in the secant column. Fill the cotangent column by reversing the values from the tangent column.