**In Chapter 11 students will: **
- understand concepts of angles
- use protractors to measure angles

**Vocabulary:**
__ray__ - a part of a line, with one endpoint, that is straight and continues in one direction
__vertex__ - the point at which two rays on an angle meet; or two or more line segments meet in a two-dimensional shape
__acute angle__ – an angle that has a measure less than a right angle
**obtuse angle** – an angle that has a measure greater than a right angle
**right angle** – an angle that forms a square corner and has a measure of 90 degrees
__degree__ - the unit used for measuring angles
**protractor** - a tool used for measuring the size of an angle
__clockwise__ - in the same direction in which the hands of a clock move
**counterclockwise** - in the opposite direction in which the hands of the clock move

**Chapter 11 Standards:***Measurement and Data (4.MD)**Geometric Measurement: Understand concepts of angle and measure angles.*Recognize angles as geometric shapes that are formed wherever two rays share a common endpoint, and understand concepts of angle measurement.

5a. An angle is measured with reference to a circle with its center at the common endpoint of the rays, by considering the fraction of the circular arc between the points where the two rays intersect the circle. an angle that turns through 1/360 of a circle is called a "one-degree angle," and can be used to measure angles.

*(CC.4.MD.5)*5b. an angle that turns through

* n* one-degree angles is said to have an angle measurement of

*n *degrees.

*(CC.4.MD.5)*6. Measure angles in whole-number degrees using a protractor. Sketch angles of specified measure.

*(CC.4.MD.6)*7. Recognize angle measure as additive. When an angle is decomposed into non-overlapping parts, the angle measure of the whole is the sum of the angle measures of the parts. Solve addition and subtraction problems to find unknown angles on a diagram in real world and mathematical problems e.g., by using an equation with a symbol for the unknown angle measure.

*(CC.4.MD.7)*