Secondary Math 2 8.1 – Triangle Basics To change the image on this slide, select the picture and delete it. Then click the Pictures icon in the placeholder to insert your own image. 8.1 – Triangle Basics

Warm-UP: with your neighbor/group Which does not belong? Why?

Warm-UP (Part 2) What is the sum of m<1, +m<2 + m<3? If m<4 = 65˚ and m<5 = 50˚, what is m<2? 1 3 2 4 5

What you will learn I will be able to classify triangles. I will be able to solve for any missing angle. I will be able to find the area for any triangle.

Classification - Sides

Classification - Angles

Classification – Practice (be specific)

The sum of the measures of the interior angles of a triangle is 180˚ Triangle Sum Theorem The sum of the measures of the interior angles of a triangle is 180˚ The sum of all the angles equals 180˚ (solve for a missing angle) 𝒎<𝟏+𝒎<𝟐+𝒎<𝟑=𝟏𝟖𝟎°

Triangle Sum Theorem EXAMPLE 90º 50º 40º

PRACTICE!!!! Solve for x. 70º x 78º 30º x

More Practice #7. Solve for x 7x- 6 𝟖𝟎° 50°

Word Problems The ladder is leaning on the ground at a 75˚ angle. At what angle is the top of the ladder touching the building?

EQUILATERAL TRIANGLE Triangle where ALL 3 sides are congruent Equilateral triangles are also equiangular (all angles are the same)

ISOSCELES TRIANGLES Triangle where 2 sides are congruent 𝐴𝐵 ≅ 𝐶𝐵 Also the two angles opposite the sides are congruent. (<𝐴≅<𝐶)

Corollary to Triangle Sum Theorem *Corollary = statement that readily follows from a theorem (doesn’t need proof, it’s like a natural statement) The acute angles of a right triangle are complementary. 𝒎<𝑨+𝒎<𝑩=𝟗𝟎°

The diagram shows a cross-legged stool The diagram shows a cross-legged stool. Calculate the angles marked by letters.

Calculate the angles marked by letters.

Area of a Triangle 𝐴= 𝑏∗ℎ 2

AREA PRACTICE