Answer: 70.5°
Solution:
Call B, the measure of the angle CBA
cos(B) = adjacent-leg / hypotenuse = 3 / 9 = 1 / 3
=> B = arc cos (1/3) ≈ 70.5°
I will calculate other measures for you, trying to cover the most common ratios: sine, cosine, tangent
1) (segment CA)^2 + (segment BC)^2 = (hypotenuse)^2
=> (segment CA )^2 = (hypotenuse)^2 - (segment BC)^2 = 9^2 - 3^2 = 81 - 9 = 72
=> segment CA = √72 = 6√2
2) sin(B) = opposite-leg / hypotenuse = 6√2 / 9 =2√2 / 3
3) sin(A) = cos(B) = 1/3
4) cos(A) = sin(B) = 2√2 / 3
5) tan(B) = opposite-leg / adjacent-leg = (2√2 / 3 ) / 3 = 2√2 / 9
6) tang(A) = 3 / (2√2 /3) = 9 /( 2√2) = 9√2 / 4