Trigonometry: Sine and Cosine

History What is Trigonometry – The study of the relationships between the sides and the angles of triangles. Origins in Astronomy, the Greek philosopher Claudius Ptolemy used table of chord ratios and their related angles were used to describe the motion of planets.

Adjacent and Opposite Sides Adjacent Side – the leg of the triangle that is next to the given angle Opposite Side – the leg of the triangle that is across from the given angle. Hypotenuse – side opposite the right angle 30 Opposite Adjacent Hypotenuse

Identify Where are the Adjacent and Opposite sides?? 2065 Opp. Adj.

Sine How do you find an unknown side length using Sine?? 20 x 15

Cosine How do you find an unknown side length using Cosine?? x

Your Calculator Make sure you are in Degree mode! Not radian mode. Key Stokes: angle, sin or sin, angle, enter 74 sin or sin 74 enter

Examples 40 7 y x