Academic
Angles
Using Angle Facts to Solve for Unknown Angles in Multi Step Problems
In this example, you are asked to find the value of x. X is imbedded in an equation that shows two of the
angles. Since we know that all the angles must add up 360 degrees, we know that if we subtract 35
and the equations without x, we will get the value of x.
1) First, I combined the equations together. 6x +19+35=360
6x+54=360
-54 -54
6x=306
6 6
x=51
Now we know that x=51, because 6 x 51 + 19 + 35 = 360.
Here are some practice problems
1)
2)
3)
Drawing Geometric Figures with Given Angles
If I gave you the degree angles 60, 40, and 80, could you draw a triangle with those degree angles? First, draw a straight line. Then, use a protracter to draw a line that is at a 40 degree angle to the first line. From there, draw a 60 degree line. Close the triangle and double check that the last angle is 80 degrees. It should look like this.
Sometimes you have to find the missing angles for geometric figures. Given the information that in a triangle all angles must add up to 180 degrees, and I tell you that two of the angles are 40 and 80, could you find the third angle? You add the two angles you know, then subtract that number from 180. Here are some practice questions.
For the following questions, find the missing angle degree (the triangles are not to size, they are simply a visual tool)
1) 37.2 , 72.6, ?
2) 45, 22, ?
3) 64, 81.7, ?
4) 28.4, 78.1, ?
5) 61.1, 39.79, ?
Identifying Geometric Figures
When doing geometry, you will need to be able to identify geometric figures in order to know what you're working with. This is a very wide subject, but we will be mainly focusing on triangles.
Classifications by Angle:
Right triangle: one right angle(90°)
Obtuse triangle: one obtuse angle(more than 90°)
Acute triangle: all angles are acute(less than 90°)
Classifications by Sides:
Isosceles triangle: exactly two congruent sides
Scalene triangle: no congruent sides
Equilateral triangle: three congrent sides
Here are some practice figures to identify.
