GETTING TO KNOW TRIANGLES 7 TH GRADE MATH BY MRS. BRUSH

 Triangles are everywhere.  They can be found bracing a bridge.

 Triangles can be found racking up billiard balls.

Triangles can be seen holding up shelves.

 A triangle is a polygon with 3 sides.  Triangles can be classified by sides.  Triangles can be classified by angles.

TRIANGLES BY SIDES  SCALENE  ISOSCELES  EQUILATERAL

SCALENE TRIANGLE  WHEN 3 PEOPLE GET ON THE SCALES TO SEE HOW MUCH THEY WEIGHT, EACH ONE WEIGHS A DIFFERENT AMOUNT. SO…………

 A scalene triangle has no equal sides. All sides are different lengths.

Isosceles Triangles  Isosceles triangles have 2 equal sides.  The angles opposite the equal sides are also equal. <B = <C AB = AC

Equilateral Triangles  All 3 sides of an equilateral triangle are equal.  Each angle of an equilateral triangle are equal.  Each angle must be 60 degrees.

 Now let’s review.  What kind of triangle has all 3 sides and angles equal?

Equilateral Triangle

 What kind of triangle has all sides a different length ?

SCALENE TRIANGLE

 What kind of triangle has 2 equal sides?

AN ISOSCELES TRIANGLE

TRIANGLES BY ANGLES AcuteRightObtuse

Acute triangles All angles are less than 90 degrees.

 A right triangle has one 90 degree angle.

OBTUSE TRIANGLE  An obtuse triangle has one obtuse angle. The obtuse angle is more than 90 but less than 180 degrees.

DISCUSSION QUESTIONS  Is it possible to have a right equilateral triangle?  Could you have a triangle that is isosceles and acute?

CREDITS  Microsoft clip art.  wwwmath.com/school/subject/practice 