Introduction to sine and cosine
The angle on the triangle in the first applet can be changed.
Change the angle in the first applet so that the triangle is similar to the triangle in the second applet.
Use the lengths given in the first applet to calculate the lengths required in the second applet.
Math vocabulary and notation is made up at some point by someone. The green and the red side have names that tie them to one of the two acute angles in a right angled triangle. The green side, opposite the angle marked, is called the 'sine of the angle'. How do you use the 'hypotenuse = 1' triangle to calculate the green side on the second triangle?
The red side, the side that touches the angle (is adjacent to the angle) is called the 'cosine of the angle'. How do you use the 'hypotenuse = 1' triangle to calculate the red side on the second triangle?
Here is some history of where the math names 'sine' and 'cosine' come from.