Trigonometric Ratios: Sin, Cos, Tan

In a right triangle, for an acute angle theta: [formula] Memory aid: SOH-CAH-TOA Also: tantheta = frac{sintheta}{costheta}

Example: In a right triangle, the side opposite theta is 5 and the hypotenuse is 13. Find sintheta, costheta, tantheta.

The SAT often asks: 'In a right triangle, sin A = frac{3}{5}. What is cos A?' Draw the triangle: opposite = 3, hypotenuse = 5, so adjacent = 4. cos A = frac{4}{5}. Recognize the 3, 4, 5 triple!