Let us prove that angle 1 is complementary to angle 3 step by step.
1. We have been given that angle 1 is complementary to angle 2.
2. Since we know that complementary angles add up to 90 degrees, therefore, by the definition of complementary
.
3. We have been also given that line segment BD bisects
.
4. By the definition of bisect
.
5. Angles are congruent if their measures, in degrees, are equal, therefore, by angle congruence postulate
.
6.
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Upon substituting
in above equation we will get,
Therefore, by substitution property of equality
.
Hence, proven that angle 1 is complementary to angle 3.