In right triangle abc, ∠a and ∠b are complementary angles and sin a = 89. what is cos b?

cos B = 0.89

Step-by-step explanation:

If ∠A and ∠B are complementary then: ∠A + ∠B = 90°

Given that sin A = 8/9 then A can be computed with the inverse of sine as follows:

∠A = arcsin(8/9) = 62.7°

Then:

62.7° + ∠B = 90°

∠B = 90° - 62.7°

∠B = 27.3°

Finally,

cos 27.3° = 0.89