Which of these equations is always true?
sin(x) = cos(x)
sin(x) = cos(90°-x)
sin(x) = cos(180°-X)
sin(x) = cos(360° - x)

sin(x) = cos(90°-x)

Step-by-step explanation:

Looking at the graphs of sin(x) and cos(x), you can see that the peaks of the graph are separated by a value of pi/2. If you convert that value into degrees, then the two graphs are separated by 90°. Another way of thinking is from the unit circle. sin(x) = 1 at 90°, and cos(x)=1 at 0°. The difference is still 90°

ab will be equal to

so far i think you have the right thing going for you just remember soh cah toh

step-by-step explanation:

sine over hypotenuse

cosine   equals adjacent

tangent over hypotenuse