Math  201920
5.12  Classify and Measure Angles
The student will
 classify and measure right, acute, obtuse, and straight angles.
Adopted: 2016
BIG IDEAS
 So that I can build a sturdy skateboard or bike trick ramp using the correct angle
 So that a pilot can use their knowledge of angles to fly and land a plane correctly
 So that a football player can throw a pass at the correct angle so the receiver can catch the ball
 So that when I park a car, I can park it correctly between the lines
UNDERSTANDING THE STANDARD
 Angles can be classified as right, acute, obtuse, or straight according to their measures.
 Angles are measured in degrees. A degree is 1/360 of a complete rotation of a full circle. There are 360 degrees in a circle.
 To measure the number of degrees in an angle, use a protractor or an angle ruler.
 A right angle measures exactly 90 degrees.
 An acute angle measures greater than zero degrees but less than 90 degrees.
 An obtuse angle measures greater than 90 degrees but less than 180 degrees.
 A straight angle measures exactly 180 degrees.
 Before measuring an angle, students should first compare it to a right angle to determine whether the measure of the angle is less than or greater than 90 degrees.
 Students should recognize angle measure as additive. When an angle is decomposed into nonoverlapping parts, the angle measure of the whole is the sum of the angle measures of the parts.

Students should understand
how to work with a protractor or angle ruler as well as available computer
software to measure and draw angles and triangles.
ESSENTIALS
The student will use problem solving, mathematical communication, mathematical reasoning, connections, and representations to
 Classify angles as right, acute, obtuse, or straight.
 Identify the appropriate tools (e.g., protractor and
straightedge or angle ruler as well as available software) used to measure and
draw angles.
 Measure right, acute, obtuse, and straight angles, using
appropriate tools, and identify their measures in degrees.
 Solve addition and subtraction problems to determine unknown
angle measures on a diagram in practical problems.
KEY VOCABULARY
Updated: May 29, 2019