Question

State a true conclusion. 1) If two planes intersect, their intersection is a line. 2) Plane R and plane S intersect. Conclusion:

Answer 1

Answer: The answer is "the intersection is a line".

Step-by-step explanation:  The concept of lines and planes that we studied in geometry are familiar to us. For example-

(i) The intersection of two lines is a point.

(ii) A plane consists of a line and a point not on the line, etc.

Like these, we have another fact that suppose there are two planes. Then we have two options

(a) They do not intersect with each other.

(b) If they do so, then their intersection is a line.

See the attached figure, there are two planes P and Q, which intersect at the line AB.

Since the given two planes intersect, the using the above fact we can say that their intersection is a line.  

Thus, the conclusion is "the intersection of two intersecting planes is a line."

Answer 2

Two planes that intersect are simply called a plane to plane intersection. When they intersect, the intersection point is simply called a line.

Therefore, Plane R and Plane S form a line when they intersect.