Match the reasons with the statements given. given: △abr = | | prove: ∠1 = ∠2 1. segment ra = segment rb, rs||ab substitution 2. ∠a = ∠b base ∠'s of isosceles triangle = 3. ∠a = ∠2 given 4. ∠b = ∠1 if lines ||, alternate interior ∠'s = 5. ∠1 = ∠2 if lines ||, corresponding ∠'s =