Solving Triangles| www.mathsisfun.com
The golden ratio (symbol is the Greek letter phi shown at left) is a special number approximately equal to 1.618 ... It appears many times in geometry, art, architecture and other| www.mathsisfun.com
Make a 3,4,5 Triangle ... Connect three lines ... And you will have a right angle (90) ... You can use other lengths by multiplying each side by 2. Or by 10. Or any multiple.| www.mathsisfun.com
Unit Circle| www.mathsisfun.com