Chapter 7 - Applications of Trigonometric Functions - Section 7.1 Right Triangle Trigonometry ; Applications - 7.1 Assess Your Understanding - Page 540: 7

$\text{True}$

For a right triangle, the Pythagorean Theorem can be applied, which shows an equation involving the three sides $a, b, \text{ and } c$ of the triangle. $$c^2=a^2+b^2$$ If we know two sides, then we can use the theorem to solve for the third. Therefore, the given statement is true.