In a right triangle that has one acute angle of 18 degrees, cos 18 degrees is congruent to?

cos (18°) = sin (72°)

Step-by-step explanation:

we know that

In a right triangle

cos (A) = sin (B)

If A and B are complementary angles

so

A+B=90°

In this problem

A=18°

B=90-18=72°

therefore

cos (18°) = sin (72°)