How do you evaluate sin(π/4)?

1 Answer
Feb 11, 2016

sqrt(2)/2

Explanation:

In the trigonometric circle pi/4 is the bisectrix between 0 and pi/2, where x=y.
By the Pythogoras theorem we know that x^2+y^2=1.

If you don't know the trigonometric circle, you can see that if one of the small angles of a rectangle triangle is pi/4, the other will be also pi/4, which implies the catets are equal.

So if x=y, you will have

x^2+y^2=1

2y^2=1

y^2=1/2

y=sqrt(1/2)=sqrt(2)/2

To get the sin of pi/4 you divide the opposite catet (sqrt(2)/2)
by the hypothenuse( 1).

You'll get sqrt(2)/2