Flashcard 18 - Mathematics: Geometric and Spatial Reasoning Flashcard Set for the TSIA2

cosine

To solve for unknown sides and angles in a right triangle, we use trigonometry—mainly sine, cosine, and tangent. With respect to an angle in the right triangle (other than the \(90^{\circ}\) angle), we define:

• Sine as the ratio of the opposite side to the hypotenuse
• Cosine as the ratio of the adjacent side to the hypotenuse
• Tangent as the ratio of the opposite side to the adjacent side

Thus, in right triangle trigonometry, the ratio of the adjacent side to the hypotenuse is known as cosine.