In many ways, trigonometry is a bridge between geometry and calculus. Trigonometry studies triangles, especially the relationships between sides and angles. In this lesson, we’ll study some important vocabulary for trigonometry and also begin our introduction to calculus.
- right angle
- theta (θ)
- angle of theta
- hypotenuse
- adjacent
- opposite
- sine
- cosine
- tangent
- trig functions
- limit
Trig Functions
In the previous unit, we learned a little about triangles. Right triangles have special properties and special names for sides and angles. Right triangles are usually drawn like in the picture below.
- The right angle (the one with the square) is the 90° angle.
- The angle marked θ is called the angle of theta. Theta (θ) is used as a variable for one of the acute angles in a right triangle.
In this kind of triangle, each side has a special name.
- Hypotenuse: The longest line, as we learned in the previous unit, is called the hypotenuse. It's always across from the right angle.
- Adjacent: In English, “adjacent” means “next to.” In a triangle, the adjacent is “next to” the angle of theta.
- Opposite: In English, one meaning of “opposite” is “across from” (like “She sat opposite the door”). In a triangle, the opposite is the line “across from” the angle of theta.
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