1. ∠C ≅ ∠B by definition of congruency
2. m∠Y by definition of obtuse angle
3. ∠C ≅ ∠A by definition of congruency
4. ∠N and ∠P are complementary angles by definition of complementary angles
Step-by-step explanation:
1. The given parameters are;
Statement Reason
ΔABC is a right triangle Given
∠A is a right angle Given
m∠B = 45° Given
m∠A + m∠B + m∠C = 180° Sum of interior angles of a triangle
m∠C = 180° - (m∠A + m∠B)
m∠C = 180° - (90° + 45°) = 45° Substitution property
m∠C = 45° = m∠B Substitution property
∠C ≅ ∠B Definition of congruency
2. Statement Reason
m∠X = 4·a + 2 Given
m∠Y = 21·a + 3 Given
∠X and ∠Y are linear pair Given
m∠X + m∠Y = 180° Sum of angles of linear pair
4·a + 2 + 21·a + 3 = 180° Substitution property
25·a + 5 = 180°
a = (180 - 5)/25 = 7
m∠Y = 21 × 7 + 3 = 150° Substitution property
m∠Y = 150° > 90
m∠Y is an obtuse angle Definition of obtuse angle
3. Statement Reason
∠A and ∠B are complementary angles Given
∠A + ∠B = 180° Definition of complementary angles
∠B and ∠C are complementary angles Given
∠B + ∠C = 180° Definition of complementary angles
∠B + ∠C = ∠A + ∠B Transitive property
∠C = ∠A Reverse of addition property of equality
∠C ≅ ∠A Definition of congruency
4. Statement Reason
ΔMNP is a right triangle Given
∠M is a right angle Given
∠M + ∠N + ∠P = 180° Sum of interior angles of a triangle
∠N + ∠P = 180° - ∠M Subtraction property of equality
∠N + ∠P = 180° - 90° = 90° Substitution property of equality
∠N + ∠P = 90° Substitution property of equality
∠N and ∠P are complementary angles Definition of complementary angles.