Question

Apply postulates and theorems to complete the statements.

If two planes intersect, then

Short answer

The blank should be filled with they form a line.

Step-by-step solution

Step 1. Select which theorem or postulate will be suitable.

Postulate 9 will be the best approach for the provided statement.

Step 2. Explain the postulate.

Postulate number 9 states that the intersection of planes helps in the formation of a line.

Step 3. Make the answer by using the explanation

The incomplete statement matches with the explanation of the postulate so the blank space should be filled with ‘they form a line’.