Exercise 3 Page 425

Two angles are complementary if the sum of their measures is 90^(∘). Since we are told that ∠1 is a complement of ∠2, we can create an equation to demonstrate this relationship. m∠ 1 + m∠ 2= 90^(∘) We can find m∠ 1 by substituting the given value, m∠2=5^(∘), into the equation.

m∠ 1 + m∠ 2= 90^(∘)

Substitute

m∠ 2= 5^(∘)

m∠ 1 + 5^(∘)= 90^(∘)

SubEqn

LHS-5^(∘)=RHS-5^(∘)

m∠ 1= 85^(∘)

The measure of m∠ 1 is 85^(∘).