Which rule explains why these triangles are similar

What two criteria are needed for triangles to be similar

An is a number that is written without a component. it is a number that is either or . an exponent is a or a number that another number is being to. the number that is being raised to a is called the . the or power tells you how many times to the base by . if an exponent is fractional then ask yourself the question: what when multiplied by itself a certain number of times will equal the number?

Which of the following statements is true? a. sin 18° = cos 72° b. sin 55° = cos 55° с. sin 72° = cos 18° d. bоth a and c.