Question

if ∠abc and ∠def are complementary, and m∠abc is equal to 20°, then what is m∠def? m∠def = ？°

Explanation:

Step1: Recall complementary - angle definition

Complementary angles add up to 90°. So \(m\angle ABC + m\angle DEF=90^{\circ}\).

Step2: Substitute the given angle value

Given \(m\angle ABC = 20^{\circ}\), then \(20^{\circ}+m\angle DEF = 90^{\circ}\).

Step3: Solve for \(m\angle DEF\)

\(m\angle DEF=90^{\circ}- 20^{\circ}=70^{\circ}\).

Answer:

\(70\)