A trigonometry question

[Cymric]

I can never remember 'opposite' and 'adjacent', so instead I remember by means of a circle with unit radius. Then the sine of an angle is simply it's y-coordinate where it intersects the circle; the cosine the x-coordinate; and the tangent y divided by x, because it should be infinite at x = 0, and that can only happen if you divide by 0. It has the advantage of working in all four quadrants too; the SOH-something rule only works in the first of the four...

[Cymric]

@Cymric - I like that, and it fits with my Maths education with the four quadrants. I guess your starting point is x=1, y=0, and your moving anticlockwise (the positive direction).

Yes. I should have added the following: 'Position the angle at the origin, with one of its 'legs' positioned on the X-axis. Extend the other 'leg' until it intersects the circle. Then the sine of the angle is the y-coordinate of the intersection point, ...'

And yes, you do move anticlockwise that way. It's rather like the opening of a book, or (even better) a spiral binder.