Measurement of Angles Level 4 In this video we will start going over simple
examples involving measurement of angles.
Let's jump straight into the first example.
According to the diagram, which two angles are congruent?
In this problem we are given two triangles and we are asked to determine which two angles
are congruent.
Recall that we can visually show that two angles are congruent by using arc marks.
The first triangle has a single arc mark at angle A and a double arc mark at angle C,
the second triangle has a triple arc mark at angle R and a single arc mark at angle
S. Two angles will be congruent if they have matching arc marks so angle A and angle S
are congruent and this is our final answer.
Let's take a look at the next example.
State the measure of each angle and classify the angle.
Angle BOC In this problem we are provided with a couple
of angles along with a protractor.
Each ray is assigned a particular angle measure.
We are asked to determine the measure of angle BOC and classify the angle based on this angle
measurement.
Recall that we can determine the measurement of an angle by computing the absolute difference
of the numbers that the rays or segments correspond with on the protractor.
In this case angle BOC is formed by ray OC which is assigned an angle measure of 90 degrees
and ray OB is assigned an angle measure of 20 degrees.
Computing the absolute difference of these two values we obtain 70 degrees for the measurement
of angle BOC.
So this angle can be classified as an acute angle.
Let's try next problem.
Angle GOH Similar to the previous problem let's locate
the sides of angle GOH.
Notice that ray OH is located at the 180 degree mark since it is aligned on the straight edge
of the protractor.
Ray OG is aligned with the 160 degree mark.
So the measure of angle GOH will be equal to the absolute difference of these two angle
measurements, simplifying the expression we obtain 20 degrees for the measure of angle
GOH.
So this angle can be classified as an acute angle.
Let's try the next problem.
Angle COA Once again let's figure out where the rays
of the angle are located on the protractor.
Ray OC is located at the 90 degree mark and ray OA is located at the 0 degree mark since
it is aligned with the straight edge of the protractor.
Calculating the absolute difference of these angles we obtain 90 degrees.
So this angle can be classified as a right angle.
Let's move along to the next example.
Angle GOB Here ray OG is aligned with the 160 degree
mark and ray OB is aligned with the 20 degree mark.
Computing the absolute difference of these angles we obtain 140 degrees.
So this angle can be classified as an obtuse angle.
Let's try the next one.
Angle HOA Here ray OH is aligned with the 180 degree
mark and ray OA is aligned with the 0 degree mark.
Computing the absolute difference of these angles we obtain 180 degrees.
So this angle can be classified as a straight angle.
Let's check out next problem.
Name a pair of congruent acute angles.
Now we are asked to determine a pair of acute angles.
Recall that acute angles are angles that measure greater than 0 degrees but less than 90 degrees.
Looking at the diagram we see that angle GOH and angle BOA are congruent acute angles since
both angles measure 20 degrees.
Angles GOC and COB are also congruent acute angles since they measure 70 degrees.
So either of these two angle pairs is an acceptable answer.
Let's try the next problem.
Name a pair of congruent right angles.
Similar to previous problem we need to identify 2 congruent angles that measure 90 degrees.
Looking at the diagram we see that angle HOC and angle COA both measure 90 degrees.
So these angles are congruent right angles.
Let's try the next problem.
Name a pair of congruent obtuse angles.
Alright now we want to identify 2 congruent obtuse angles, recall that an obtuse angle
is greater than 90 degrees but less than 180 degrees.
Looking at the figure we see that angle HOB and angle GOA both measure 160 degrees.
So these angles are congruent obtuse angles.
Alright now let's go over problems that require us to find parts of a degree.
Change 41.4 degrees to degrees and minutes.
In this problem we are given a degree measurement and we are asked to convert it to degrees
and minutes.
Recall that minutes and seconds are used when we have a degree measurement that has a fraction
of a degree in this example we have 4 tenths of a degree as our fraction.
We want to convert this fractional part of a degree into minutes.
Since there are 60 minutes in one degree we can determine the number of minutes in 0.4
degrees by simply taking the decimal and multiplying it by 60 doing that we obtain 24 minutes.
So this angle measure can be written as 41 degrees 24 minutes and this is our final answer.
Let's go over the final example.
Change 60 degrees 45 minutes to degrees.
In this problem we are given an angle measurement in degrees and minutes and we are asked to
convert it to degrees.
In order to convert this measurement we need to change 45 minutes to a fractional part
of a degree and add it to 60 degrees.
Once again since 60 minutes equals 1 degree we can take 45 and divide it by 60.
We then reduce the fraction obtaining the following.
So 60 degrees 45 minutes can be written as 60 and three quarters degrees or alternatively
as 60.75 degrees when we convert the fraction into a decimal and this is our final answer.
Alright in our next video we will go over slightly more challenging examples.
For more infomation >> Mỹ sẽ thất bại trong việc ngăn chặn Trung Quốc ở Biển Đông - Duration: 30:10. 
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