1. The problem is to write a proof in columnar format, which typically involves two columns: one for statements and one for reasons. 2. The columnar proof format helps organize logical steps clearly, showing each statement alongside its justification. 3. For example, if proving that $\angle A + \angle B = 90^\circ$ in a right triangle, the left column lists each step (statements), and the right column lists reasons (definitions, postulates, theorems). 4. To write a proof in columnar format: - Step 1: Write the given information in the first row under statements. - Step 2: Write the reason for the given information (e.g., "Given") in the corresponding reason column. - Step 3: Proceed with each logical step, writing the statement and its reason side by side. 5. This format clarifies the flow of logic and makes it easier to follow and verify each step. 6. Without a specific proof provided, this is the general method to write any proof in columnar format.