Wood Technology & Processes

Self-Check Math Quizzes : Self-Check Math Quizzes

Math Activity 5

Angles


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Woodworkers use angles in measurement, layout, and installations. An angle is formed by two lines that meet at a given point. A countertop meets the wall to form an angle. The pieces of a picture frame also meet at an angle.

Angles are measured in degrees. An acute angle is an angle that is less than 90 degrees. A right angle measures exactly 90 degrees. A symbol that looks like a square may be drawn on the angle to indicate that it is a right angle. An obtuse angle measures more than 90 degrees but less than 180 degrees.

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Two angles are complementary if their sum totals 90 degrees. When two angles total 180 degrees, the angles are supplementary.

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When two straight lines intersect, the angles next to each other total 180 degrees and the angles opposite each other are equal.

Terms, Symbols, & Abbreviations
angle—formed when two lines meet at a given point
acute angle—an angle that measures less than 90 degrees
right angle—an angle that measures exactly 90 degrees
obtuse angle—an angle that measures more than 90 degrees
complementary angles—two angles whose sum is 90 degrees
supplementary angles—two angles whose sum is 180 degrees
degree symbol = °

Practice Exercise

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Identify the angles in the drawing.

  • Angle A is more than 90 degrees and less than 180 degrees. Therefore it is an obtuse angle.
  • Angle B is less than 90 degrees. It is an acute angle.
  • Angle C is exactly 90 degrees. It is a right angle. Note the symbol where the two lines meet.

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Identify the complementary and supplementary angles.

  • The two angles in A add up to a straight line, which is 180 degrees. Therefore these angles are supplementary.
  • The two angles in B make up a right angle, which is 90 degrees. These angles are complementary.


Problem Exercises

1.

The angles formed when studs are nailed correctly to the top and bottom plates of a wall are
A)acute angles.
B)right angles.
C)obtuse angles.
D)supplementary angles.
2.

One example of an obtuse angle is the angle formed
A)by two sides of a gable roof.
B)by a stud nailed to a sill plate.
C)by two walls joined at a corner.
D)by a stair stringer and the floor underneath it.
3.

An acute angle may be formed by the
A)top of a roof truss.
B)coped end of molding.
C)riser and tread on a stair.
D)intersection of two walls.
4.

Two angles are complementary when their sum equals
A)180 degrees.
B)120 degrees.
C)90 degrees.
D)45 degrees.
5.

A 45-degree angle to be cut for a miter joint is a(n)
A)acute angle.
B)right angle.
C)obtuse angle.
D)complementary angle.
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