McGraw Hill Integrated II, 2012
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McGraw Hill Integrated II, 2012 View details
4. Trigonometry
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Exercise 75 Page 659

Use the Triangle Inequality Theorem to determine whether the given side lengths can form a triangle.

Triangle? Yes.
Acute, Obtuse, or Right? Obtuse.
Explanation: See solution.

Practice makes perfect
First, we want to determine whether the given set of numbers can be the measures of the sides of a triangle. To do that we will use the Triangle Inequality Theorem. We have to check if the sum of each two sides is greater than the third side. 13+30>& 35 âś“ 13+35>& 30 âś“ 30+35>& 13 âś“ As we can see, the given side lengths can form a triangle. Now, we need to determine if this triangle is acute, right, or obtuse. To do so, we will compare the square of the largest side length to the sum of the squares of the other two side lengths. Let a, b, and c be the lengths of the sides, with c being the longest.
Condition Type of Triangle
a^2+b^2 < c^2 Obtuse triangle
a^2+b^2 = c^2 Right triangle
a^2+b^2 > c^2 Acute triangle
Let's now consider the given side lengths 13, 30, and 35. Since 35 is the greatest of the numbers, we will let c be 35. We will also arbitrarily let a be 13 and b be 30. 13^2+30^2 ? 35^2 Let's simplify the above statement to determine whether the left-hand side is less than, equal to, or greater than the right-hand side.
13^2+30^2 ? 35^2
169+900 ? 1225
1069 < 1225
Referring back to our table, we can conclude that the side lengths 13, 30, and 35 form an obtuse triangle.