Use the premises and conclusion to answer the questions. premises: if the sides of a triangle are the same length, then the triangle is an equilateral triangle. if a triangle is an equilateral triangle, then the measure of each angle is 60°. conclusion: if the sides of a triangle are the same length, then the measure of each angle is 60°. is the argument valid? why or why not? the argument is not valid because the premises are not true. the argument is not valid because the conclusion does not follow from the premises. the argument is valid by the law of syllogism. the argument is valid by the law of detachment.