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Big Ideas Math: Modeling Real Life, Grade 8

BI

Big Ideas Math: Modeling Real Life, Grade 8 View details

4. Rational Numbers

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Exercise 4 Page 399

The sum of the measures of the interior angles of a triangle is 180^(∘).

90^(∘), 15^(∘), and 75^(∘)

Practice makes perfect

We want to find the measures of the angles in the given triangle.

triangle

To find these angle measures, we will first recall a key piece of information!

Interior Angle Measures of a Triangle
The sum of the measures of the interior angles of a triangle is 180^(∘).

With this rule, we can write an equation connecting the measures of the angles of our triangle. Remember that a right angle measures 90^(∘). x^(∘) + 15^(∘) + 90^(∘) = 180^(∘) Let's solve the equation and find the value of x. For simplicity, we will not write the degree symbol.

x + 15 + 90 = 180

▼

Solve for x

Add terms

x + 105 = 180

LHS-105=RHS-105

x = 75

The measure of the third angle is 75^(∘).

triangle

Subchapter links

Try It p.396-397

Self-Assessment for Concepts & Skills p.397-398

Review & Refresh p.399

Concepts, Skills, & Problem Solving p.399-400