http://www.ck12.org Chapter 4. Basic Triangle Trigonometry
4.3 Special Right Triangles
Here you will review properties of 30-60-90 and 45-45-90 right triangles.
The Pythagorean Theorem is great for finding the third side of a right triangle when you already know two other
sides. There are some triangles like 30-60-90 and 45-45-90 triangles that are so common that it is useful to know the
side ratios without doing the Pythagorean Theorem each time. Using these patterns also allows you to totally solve
for the missing sides of these special triangles when you only know one side length.
Given a 45-45-90 right triangle with sides 6 inches, 6 inches andxinches, what is the value ofx?
Watch This
MEDIA
Click image to the left for use the URL below.
URL: http://www.ck12.org/flx/render/embeddedobject/58104http://www.youtube.com/watch?v=681WWiNxMIQ Khan Academy: Intro to 30 60 90 Triangles Geometry
MEDIA
Click image to the left for use the URL below.
URL: http://www.ck12.org/flx/render/embeddedobject/58106http://www.youtube.com/watch?v=tSHitjFIjd8 Khan Academy: 45 45 90 Triangles
Guidance
A 30-60-90 right triangle has side ratiosx,x
√
3 , 2 x.