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Big Ideas Math: Modeling Real Life, Grade 8

BI

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

2. Angles of Triangles

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Exercise 1 Page 112

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

25^(∘), 74^(∘), and 81^(∘)

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!

Angle Sum 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. x^(∘)+ 81^(∘)+ 25^(∘)=180^(∘) Let's solve the equation and find the value of x. For simplicity, we will not write the degree symbol.

x+81+25=180

Add terms

x+106=180

LHS-106=RHS-106

x=74

The measure of the angle is 74^(∘).

triangle

Subchapter links

Try It p.112-113

Self-Assessment for Concepts & Skills p.113

Self-Assessment for Problem Solving p.114

Review & Refresh p.115

Concepts, Skills, & Problem Solving p.115-116