For a right triangle abc, you are told that cos a = x and sin a = y. which option below gives an expression that is equivalent to tan a? a. x/y b. y/x c. x/√x^2+y^2 d. y/√x^2+y^2

Draw a right triangle ABC so that m∠C = 90°
The lengths are:
Side a is opposite ∠A,
Side b is opposite ∠B,
Side c (the hypotenuse) is opposite ∠C

Because cos A = x, therefore
x = b/c  => b = cx                     (1)
Because sin A = y, therefore
y = a/c  => a = cy                     (2)

By definition,
tan A = a/b
          = (cy)/(cx)
          = y/x

 b. y/x