Question

Let ∠1 , ∠2 , ∠3 , and ∠4 have the following relationships. ∠1 and ∠2 are vertical angles. ∠3 and ∠4 are right vertical angles. ∠3 is adjacent to both ∠1 and ∠2 . What is the sum of the measure of ∠4 and the measure of ∠1 minus the measure of ∠2 ?

Answer 1

Since ∠1 and ∠2 are vertical angles, they have equal measure. And since ∠3 and ∠4 are right vertical angles, they have measure 90° each.

Since ∠3 is adjacent to both ∠1 and ∠2, we can say that:

∠1 + ∠3 = 180°

∠2 + ∠3 = 180°

Adding these two equations together:

∠1 + ∠2 + 2∠3 = 360°

Substituting the values we have:

∠1 + ∠2 + 2(90°) = 360°

∠1 + ∠2 + 180° = 360°

Solving for ∠1 + ∠2:

∠1 + ∠2 = 180° - 180° = 0°

Finally, the sum of the measure of ∠4 and the measure of ∠1 minus the measure of ∠2 is:

∠4 + (∠1 - ∠2) = 90° + (∠1 - 0°) = 90° + ∠1

So the answer is 90° + ∠1.