Right Triangle Side & Angle Calculator

Solve a right triangle from one acute angle and one side using sine, cosine, and tangent.

Last updated: June 2026 | By Patchworkr Team

Angle (degrees)

Adjacent Leg

Math check: opposite = adjacent x tan(theta), hypotenuse = adjacent / cos(theta)

Result

Enter a real number.

Formulas

opposite = adjacent x tan(theta)

hypotenuse = adjacent / cos(theta)

opposite = hypotenuse x sin(theta)

adjacent = hypotenuse x cos(theta)

How to Use It

Choose whether you know the adjacent leg or the hypotenuse.
Enter an acute angle strictly between 0 and 90 degrees.
Enter the known side length and read the complete triangle from the result panel.

Worked Example

If the angle is 35 degrees and the adjacent leg is 5, then the opposite leg is about 5 tan(35 degrees) = 3.5009 and the hypotenuse is 5 / cos(35 degrees) = 6.1039.

The two acute angles always add to 90 degrees, so the other angle is 55 degrees.