Question

1. in parallelogram abcd, what is the relationship between angle a° and angle b°?

Explanation:

Step1: Recall the property of parallelogram

In a parallelogram \(ABCD\), \(AD\parallel BC\).

Step2: Use the property of consecutive - interior angles

When two parallel lines (\(AD\) and \(BC\)) are cut by a transversal (\(AB\)), the consecutive - interior angles (\(\angle A=a^{\circ}\) and \(\angle B = b^{\circ}\)) are supplementary.
By the supplementary - angle formula \(a + b=180\), so \(a^{\circ}+b^{\circ}=180^{\circ}\).

Answer:

C. \(a^{\circ}+b^{\circ}=180^{\circ}\)