Q11. Sin and Cos

If Sin 30 = X, what is Cos 60 in terms of X?

A) 1/X

B) 2X

C) X/2

D) X

Explanation

This is a definition you should just know for the exam:

Sin X = Cos (90 - X). In a right triangle, the Sin of one angle will always be the Cos of the other angle. Take a look at the triangle below. You should understand why they’re the same and note that A + B = 90. It seems basic but this concept shows up over and over on the exam.

Sin A = X/Z

Cos B = X/Z

A = (90 - B)

A + B = 90

Lesson

In addition to grasping the portion above, you should know the acronym SOHCAHTOA for memorizing the formulas for Sin, Cos, Tan.

SOHCAHTOA

Sin = Opposite / Hypotenuse

Cos = Adjacent / Hypotenuse

Tan = Opposite / Adjacent

Want more practice questions? Check out the Worthington Prep SAT Tutoring Questions page.