Basic Technical Mathematics, 11th Edition

4.4 The Right Triangle

• Solving a Triangle • Cofunctions • Procedure for Solving a Right Triangle

We know that a triangle has three sides and three angles. If one side and any other two of these six parts are known, we can find the other three parts. One of the known parts must be a side, for if we know only the three angles, we know only that any triangle with these angles is similar to any other triangle with these angles.

EXAMPLE 1 Parts of a triangle

Assume that one side and two angles are known, such as the side of 5 and the angles of $35\hspace{0.17em}°\hspace{0.17em}$ and $90\hspace{0.17em}°\hspace{0.17em}$ in the triangle in Fig. 4.28. Then we may determine the third angle $\alpha$ by the fact that the sum of the angles of a triangle is always $180\hspace{0.17em}°\hspace{0.17em}$. Of all possible similar triangles having the three ...