Download U9-04 Say Hello to Triangles u9h04

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1
Say Hello to Triangles and Friends
a)
Name ________________________
Measure the angles of triangle ABC below. To measure accurately, you will probably have to extend the
sides. If you find this to be confusing, first trace BAC in ink and then measure it. Do the same with the
other angles in a different color. Label the angles inside the triangle as in this little triangle:
Remember: bomber sights, line up zero, and count.
b) Measure the sides of triangle ABC to the nearest 1/16 of an inch. Label in the blanks on the outside of the
triangle.
2
a)
Add the measures of the three angles of triangle ABC in problem 1. Total degrees = _____
b) The sum of the measures of the three angles of any triangle should be 180°. If the total of the three are
not close to 180°, then you made a mistake while measuring. Recheck your work, and if you're still stuck,
just ask for help.
c)
Which angle in triangle ABC is obtuse? ______________
3) Now I'd like you to go back and measure the sides of  ABC above in centimeters, to the nearest tenth of a
centimeter, such as 3.6 cm. Write your measurements here:
AB = _______________ AC = ______________ BC = ____________
By the way, when we write the names of two points side by side, as in AB, that means the distance between the
points. So AB means the distance from point A to point B.
4) Measure and label the three angles of this triangle. Check to see if they add up to 180°.
5) Draw a
square with sides that are 4.5 centimeters long.
Important: Every time you measure a segment or an angle, mark what you measured, but only mark
those things.
Often students mark much more than they measured, if you do this right, you will only have to label four more
sides or angles.
That will let other people know what you have done. Don't forget to mark the right angles with the special mark.
6
a)
Draw an accurate rectangle with a length of 4 3/8 inches and a height of 2 3/16". Every time you
measure a segment or an angle, mark what you measured. Again you will have to label four things.
b) Draw and measure the length of the
c)
diagonal of the rectangle.
If you drew the rectangle correctly, the diagonal should be nearly 47/8" long. How far off from the correct
length was your measurement?
I was off by __________ .
d) Now find your percent of error; it's a
less than or
more than problem. You will also probably
need to use parentheses to enter the fractions into your calculator.
____ _____
=
___________%
47/8
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page 3
Say Hello to Triangles and Friends
Name ________________________
7) Draw an accurate version of the triangle described below. Follow these steps and again label everything you
measure.
a) Starting at B, measure to the right 9 centimeters, and label it point A.
b) From point B, draw a 25° angle slanting to the right (The ray will extend above the line segment AB you
just drew). Label your 25˚ angle with its measurement.
c) From point A, draw a 55° angle slanting to the left (or above the segment again).
d) Label the point of intersection of the two lines C.
8
a)
Measure and label angle C in the triangle you drew in problem 7. ___________
Check that the measures of the three angles add up to 180.
b) Is – C an acute or an obtuse angle?___________ Why did you choose that answer?
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c)
On the triangle label the lengths of sides BC and AC, in centimeters.
a)
Draw a right triangle with a side AB equal to 23/4 inches and an angle of 17 at B, as shown in the sketch
below. First, label the two measurements you know on the sketch to help you.
b) As you draw the triangle, label everything you measure.
c)
10 a)
Measure and label angle C and sides AC and CB, in inches. Check that the angles add up to 180°.
Here's a real challenge for you, but you can do it because you know how to think. Draw the trapezoid
sketched below.
First label these measurements on the sketch: A = 120,  ABD = 135, C = 60. Since the
measures of the four angles of a trapezoid add up to 360°, the measure of D should be ________˚.
Also on the sketch, label AC = 6.3 cm, CD = 12.6 cm, and DBH = 45.
Now study the sketch to determine where to start
your drawing. Label everything as you go.
b) Line BH is called the height of the trapezoid.
Measure and label BH to the nearest 1/16 of an inch. __________________