In ABC, angle C is a right angle. Which statement must be true

Answer:
a
Step-by-step explanation:
a because the the sin is opposite divided by hypotenuse and the opposite of a is 12 and the hypotenuse is 13 so sin a would be 12/13
this is equals to the cosine of b because cos is adjacent/hypotenuse and the adjacent of b is 12 and the hypotenuse is 13 so cos b would be 12/13
hope this helps :)