Final answer:
The size of angle x is 138°. A protractor is a semi-circular tool used to draw and measure angles. It is marked with degrees from 0 to 180 degrees. It can be directly used to measure any angle from 0 to 360 degrees. The markings are made in two ways, 0 to 180 degrees from right to left and vice versa.
Step-by-step explanation:
In the given diagram, we have a straight line AB with angle x. We are given that angle A is 42° and angle B is 29°. Since angle A and angle x form a straight line, we can find angle x by subtracting angle A from 180°.
Angle x = 180° - angle A
Angle x = 180° - 42°
Angle x = 138°
Measuring angles is a significant topic in geometry. An angle can be measured using a protractor, precisely. An angle is measured in degrees, hence its called ‘degree measure’. One complete revolution is equal to 360 degrees, hence it is divided into 360 parts. Each part of the revolution is a degree. If we know how to measure angle, then it will be very easy to construct an angle using a protractor.
Any angle whether it is acute, obtuse, reflex, or right angle, can be measured using a protractor. Although based on the right angle, we are able to differentiate between acute, obtuse or reflex angles. But if we have two acute angles to measure, then we cannot determine the greater angle among the two. Therefore, we have to use a protractor to measure the angles accurately.