Question

Given the information in the diagram below, find the measure of angle N. Use RACE and complete sentences to show how you found this answer. In your written response, include key vocabulary terms.

Answer 1

m<N = 76°

Explanation:

Given:

∆JKL and ∆MNL are isosceles ∆ (isosceles ∆ has 2 equal sides).

m<J = 64° (given)

Required:

m<N

SOLUTION:

m<K = m<J (base angles of an isosceles ∆ are equal)

m<K = 64° (Substitution)

m<K + m<J + m<JLK = 180° (sum of ∆)

64° + 64° + m<JLK = 180° (substitution)

128° + m<JLK = 180°

subtract 128 from each side

m<JLK = 180° - 128°

m<JLK = 52°

In isosceles ∆MNL, m<MLN and <M are base angles of the ∆. Therefore, they are of equal measure.

Thus:

m<MLN = m<JKL (vertical angles are congruent)

m<MLN = 52°

m<M = m<MLN (base angles of isosceles ∆MNL)

m<M = 52° (substitution)

m<N + m<M° + m<MLN = 180° (Sum of ∆)

m<N + 52° + 52° = 180° (Substitution)

m<N + 104° = 180°

subtract 104 from each side

m<N = 180° - 104°

m<N = 76°