The size of the acute angles A and B in the right triangle control the length of the triangle sides. Similarly, the length of the sides a and b control the sizes of the acute angles (Figure C-246). Therefore, the size of angles and the length of sides may be expressed in terms of each other. This is to say that for a given specified length of sides, as measured in linear units, the acute angles must be a corresponding size, as measured in degrees of arc.