Marked June 7th


Definition: Triangles are three sided polygons, with angles adding up to 180 degrees.


Types of Triangles There are many different types of triangles including: equilateral, isosceles, scalene, right, obtuse, and acute.

Equilateral Triangle - An equilateral triangle is a triangle with three equal side lengths and three equal angles of 60 degrees.

Isosceles Triangle
An isosceles triangle has only two equal side lengths and two equal angles.


Scalene Triangle
A scalene triangle has no equal sides, and no equal angles.


Right Angle Triangle

A right angle triangle has one 90° internal angle.The side opposite to the right angle is the hypotenuse which it is the longest side in the right triangle. The other two sides are the legs of the triangle.
external image hypotenuse.gif
Obtuse Angle Triangle
A obtuse angle triangle has one internal angle that is greater than 90°. It is also an Oblique triangle ( no internal angle equal to 90° )
Acute Angle Triangle
An acute angle triangle has no angles greater then 90°. It is also and oblique triangle.


Perimeter & Area

To calculate perimeter of a triangle we use P=s+s+s.
Remember to always use units, and never put a ² or a ³ because those are for area and volume

To calculate the area of a triangle we use A=bh/2
Remember to include units, the ² behind your units, ie: cm², m², km², and to divide by 2 at the end!area_triangle.jpg


Pythagorean Theorem

In math, we use Pythagorean theorem to find the missing side of a right angle triangle. For example:
Ok, so if we wanna find the missing side length, or "c", we use c²=a²+b²
( A and B can be any measurement that is there on the line, it doesn't matter the order, but C will always be the hypotenuse)
c=6.4 (rounded) -or- /41

There is also a couple other ways in solving a triangles missing sides rather than using the Pythagorean theorem.

  • Sines: sin A = a/c, sin B = b/c.
  • Cosines: cos A = b/c, cos B = a/c.
  • Tangents: tan A = a/b, tan B = b/a.

Meaning of the word...
Sines: Ratio of the length of the side opposite the given angle to the length of the hypotenuse of a right-angled triangle
Cosines: Ratio of the adjacent side to the hypotenuse of a right-angled triangle
Tangents: Ratio of the opposite to the adjacent side of a right-angled triangle
Adjacent: Things are next to each other. (Beside)

Real World Application

There is many other uses for triangles besides just math, they are used in lots of modern day structures like housing, bridges, electric pylons, and artwork can also be used in flags and signs.
triangle4.jpgexternal image 800px-Flag_of_the_Czech_Republic_%28bordered%29.svg.png

external image star_of_david_lg.jpg
Triangles (2005). Retrieved December 10, 2008, from

Joyce, D. E. (1999). Right Angles. Retrieved December 18, 2008.


scalene triangle -
right angle triangle -
obtuse angle triangle -
acute angle triangle - roof truss picture -
other triangle-

Real World Application Pictures:
Created By:
Brandon E
Jared W
Will H