# Trigonometry – Sine function (sin)

## S-O-H

The sine function of an angle is a trigonometric function that relates the ratio of the length of the side opposite the given angle to the length of the hypotenuse in a right triangle. It is denoted by the symbol “sin” and is used extensively in mathematics and physics to describe the relationships between angles and the sides of right triangles.

In a right triangle, which is a triangle that has one 90-degree angle (a right angle), the sine of an angle θ (typically measured in degrees or radians) is defined as:

Here’s what these terms mean:

1. Opposite side: This is the side of the triangle that is opposite to the angle θ that you’re interested in.
2. Hypotenuse: The hypotenuse is the longest side of the right triangle and is opposite the right angle.

The sine function gives you the relationship between the angle θ and the ratio of the lengths of these two sides. It essentially tells you how high or low a point on the unit circle is when you measure from the origin and travel along the circle by the given angle θ.

Sine is a special number for triangles. When you have a really small angle, sine is like 0 because there’s almost nothing there. But when you make the angle really big, like 90 degrees, sine becomes 1 because it’s as big as it can get.

Then, when you start making the angle smaller again, sine gets smaller too, and when the angle is back to 0, sine goes back to 0. But if you go all the way to 180 degrees, sine becomes -1 because it’s big but in the opposite direction.

And sine keeps going up and down between -1 and 1 as you change the angle.

The sine function is a fundamental tool in trigonometry and has various applications in science and engineering, including wave analysis, oscillations, and geometry.