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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 9 Page 115

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

30^(∘), 60^(∘), and 90^(∘)

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. Recall that the measure of a right angle is 90^(∘). x^(∘)+ 30^(∘)+ 90^(∘)=180^(∘) Let's solve the equation and find the value of x. For simplicity, we will not write the degree symbol.

x+30+90=180

Add terms

x+120=180

LHS-120=RHS-120

x=60

The measure of the angle is 60^(∘).

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