POLYGONS Polygon is a closed figure madeup of

POLYGONS

Polygon � is a closed figure made-up of three or more line segments

Is this a polygon? Why?

Is this a polygon? Why?

Is this a polygon? Why?

Is this a polygon? Why?

Is this a polygon? Why?

Numbers of sides 3 4 5 6 7 8 9 10 Name Triangle Quadrilateral Pentagon Hexagon Heptagon Octagon Nonagon Decagon

Triangle – a 3 -sided polygon

Kinds of triangles (according to sides) � 1. scalene triangle – a triangle with no equal sides

Kinds of triangles (according to sides) � 2. isosceles triangle – a triangle with two equal sides

Kinds of triangles (according to sides) � 3. equilateral triangle – a triangle with three equal sides

Kinds of triangles (according to angles) � 1. acute triangle – a triangle with three acute angles

Kinds of triangles (according to angles) � 2. right triangle – a triangle with one right angle

Kinds of triangles (according to angles) � 3. obtuse triangle – a triangle with one obtuse angle

Take note: If a triangle has one right angle and two equal sides, we can call that triangle right isosceles triangle.

Take note: If a triangle has only acute angles and no equal sides, we can call that triangle acute scalene triangle.

Take note: If a triangle has two equal sides and one obtuse angle, we can call that triangle obtuse isosceles triangle.

Take note: Notice that an angle cannot be obtuse and equilateral at the same time. An equilateral triangle cannot have an obtuse angle because all 3 angles in an equilateral triangle measure 60 degrees.

In an isosceles triangle:

Analyze and solve. � 1. If ABC is a right triangle, find n. n

Analyze and solve. �

Analyze and solve. � 3. Find the missing angle ?

Analyze and solve. � 4. The angles of a triangle have a ratio of 3 : 4 : 5. Find each angle.

Analyze and solve. �