Angles In a Triangle

Angles In a Triangle - introduction

*remember to read each slide carefull!

Basic rules:

angles in a triangle all add up to 180^o. It cannot be more or less than 180^o.

Types of triangles

• Isosceles: - 2 sides are equal (in length), 2 angles are equal

• Equilateral: - all sides and angles are equal

• scalene: no sides are the same length and no angles are equal.

• right-angled triangle: one of the angles is 90^o

• right-angles isosceles triangle: an isosceles triangle with one right angle

Open Ended

This triangle has 2 equal angles that are 60^o. What type of triangle is this?

Explanation

The answer you could write is an equilateral triangle! We know that 2 of the angles in the triangle is both 60^o. Since all angles in a triangle add up to 180^o, the last angle must also be 60^o! (60+60+60 = 180)

Obtuse, Acute and Right triangles

• obtuse triangle: a triangle that has an angle that is >90^o (larger than 90^o)

• acute triangle: a triangle that has all angles that are <90^o (smaller than 90^o)

• right triangle: a triangle that has an angle that is 90^o (equal to 90^o)

Take a careful look at this image, it will help you with your next question

Multiple Choice

what type of triangle was in the image shown on the slide before?

• equilateral triangle

• acute triangle

• right triangle