The sum of the three angles of a triangle is 180 degrees
If it is a right angle triangle one angle must be 90 degrees
All u have to do is 180-90- (the angle u already know)= unknown angle (third angle)
Just like regular numbers, angles can be added to obtain a sum. Sometimes we can determine a missing angle because we know that the sum must be a certain value. Remember -- the sum of the degree measures of angles in any triangle equals 180 degrees. Below is a picture of triangle ABC, where angle A = 60 degrees, angle B = 50 degrees and angle C = 70 degrees.
If we add all three angles in any triangle we get 180 degrees. So, the measure of angle A + angle B + angle C = 180 degrees. This is true for any triangle in the world of geometry. We can use this idea to find the measure of angle(s) where the degree measure is missing or not given.
Sample A
In triangle ABC below, angle A = 40 degrees and angle B = 60 degrees. What is the measure of angle C?
We know that the sum of the measures of any triangle is 180 degrees. Using the fact that angle A + angle B + angle C = 180 degrees, we can find the measure of angle C.angle A = 40
angle B = 60
angle C = we don't know.
To find angle C, we simply plug into the formula above and solve for C.A + B + C = 180
C = 180 - A - B
C = 180 - 40 - 60
C = 80
To check if 80 degrees is correct, let's add all three angle measures. If we get 180 degrees, then our answer for angle C is right.
Here we go:40 + 60 + 80 = 180
180 = 180...It checks!
You don't always have to plug in those values to the equation and solve. Once you're comfortable with this sort of problem you'll be able to say "okay, 40 + 60 =100, so the other angle has to be 80!" and it's much quicker.
Sample B
If a triangle is equiangular, what is the degree measure of each of its angles?
Remember, all angles of an equiangular triangle have equal measure. Let x = the degree measure of each angle. Triangles have three vertices and so we will add x THREE times.
We have this:x + x + x = 180
3x = 180
x = 60
Makes sense, right? If all the angles are equal, and they add up to 180, then it has to be 60 degrees!
NOT USFULL TO LONG BIA
The missing angle measure is 100 degrees.
77. The sum of the three angles in a triangle equal the sum of 180 degrees
Third angle would be 46 degree. 180-44-90 =46
A triangle with the third angle that measures 30 degrees.This triangle is not isosceles nor equilateral but has one obtuse angle.
The three of the sum to 180 degrees so 180 - (147.12 + 30.19) = 2.69 degrees.
The third angle measures 18 degrees.
The missing angle measure is 100 degrees.
The third angle is 34.5 degrees
105
The third angle is (128 degrees) minus (the second angle).
63
77 degrees
...a right triangle.
45 degrees.
25 degrees
96˚all angles to a triangle equals 180˚
90 degrees