# How to Use Trigonometry in Carpentry ••• Jean-philippe WALLET/iStock/GettyImages

Trigonometry is something that most people say they can't do. The funny part is that it is really easy. Carpentry calls for trigonometry more than you might think. Every time a carpenter makes an angled cut, the measurement of the angle or the adjoining lines must be figured out. You could do this the slow (and potentially wrong) way, or you could use trigonometry. Here is the easy “trigonometry” way to figure it out.

Learn the trigonometric function for a right triangle. sine of the Angle = opposite hypotenuse cosine of the Angle = adjacent hypotenuse tangent of the Angle = opposite Adjacent

When trying to determine the length of the opposite you would use the following equation:
tan 55 Deg = opposite 100” 100” x tan 55 Deg = opposite 100’ x 1.42 = opposite opposite = 142”

When trying to determine the length of the hypotenuse you would use the Pythagorean theorem: a2 + b2 = c2 1002 + 1422 = c2 c2 = 30164 c = 173.68”

If you need to know the measurement of the final angle, you must first know that the angles add up to 180 Degrees.
90 Deg + 55 Deg = 180 Deg – unknown 145 Deg = 180 Deg – unknown unknown = 35 Deg

#### Things You'll Need

• Measuring tape
• Square