4.1. Triangle Sum Theorem http://www.ck12.org
Example B
Show why Theorem #1 is true.
4 ABCabove is an example of an equiangular triangle, where all three angles are equal. Write an equation.
m^6 A+m^6 B+m^6 C= 180 ◦
m^6 A+m^6 A+m^6 A= 180 ◦
3 m^6 A= 180 ◦
m^6 A= 60 ◦Ifm^6 A= 60 ◦, thenm^6 B= 60 ◦andm^6 C= 60 ◦.
Example C
Use the picture below to show why Theorem #2 is true.
m^6 O= 41 ◦andm^6 G= 90 ◦because it is a right angle.
m^6 D+m^6 O+m^6 G= 180 ◦
m^6 D+ 41 ◦+ 90 ◦= 180 ◦
m^6 D+ 41 ◦= 90 ◦
m^6 D= 49 ◦Notice thatm^6 D+m^6 O= 90 ◦because^6 Gis a right angle.
Watch this video for help with the Examples above.
MEDIA
Click image to the left for use the URL below.
URL: http://www.ck12.org/flx/render/embeddedobject/52609