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Trigonometry: Sine and Cosine. History. What is Trigonometry The study of the relationships between the sides and the angles of triangles.
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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 Hypotenuse Opposite 30 Adjacent
Identify • Where are the Adjacent and Opposite sides?? Opp. Opp. Adj. 20 65 Adj.
Sine • How do you find an unknown side length using Sine?? 15 20 x
Cosine • How do you find an unknown side length using Cosine?? x 20 15
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 x y 7