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.

Standard:

Math.4.MD.5b or 4.MD.C.5.B

Description:

An angle that turns through n one-degree angles is said to have
an angle measure of n degrees.

Standard:

Math.4.MD.6 or 4.MD.C.6

Description:

Measure angles in whole-number degrees using a protractor. Sketch
angles of specified measure.

Standard:

Math.4.MD.7 or 4.MD.C.7

Description:

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.