AI Tutor
Look at the corner of a sheet of paper or a book cover. It makes a sharp square corner called a right angle, which measures exactly 90∘90^\circ.
When you draw a line splitting that square corner into two smaller pieces, those pieces have a special connection.
What special math name do we give to two angles that fit together into a perfect corner?

The 90-Degree Rule

Two or more angles are called complementary angles when their measurements add up to exactly 90∘90^\circ.
Because the whole corner is 90∘90^\circ, the parts must always equal the whole: Part+Part=90∘\text{Part} + \text{Part} = 90^\circ.
This rule is known as the Additive Angle Property: the measure of an entire angle is equal to the sum of the measures of its non-overlapping adjacent decomposed parts sharing a common vertex (m∠AOC=m∠AOB+m∠BOCm\angle AOC = m\angle AOB + m\angle BOC).
How do you find one missing piece if you already know the other?

Finding a Missing Angle

Imagine a right angle split into two parts: one angle measures 35∘35^\circ, and the other angle is mystery angle xx.
To find the missing angle, subtract the angle you know from 90∘90^\circ: 90∘−35∘=55∘90^\circ - 35^\circ = 55^\circ.