quote:Original post by cedricl
Could you write the intermediary steps? I''m missing something, here.
You can do it geometrically. Draw a unit circle centre the origin. Draw the line x = -0.2. It crosses the circle at two points. The one we are interested in is in the positive y quadrant. It has coordinates (-0.2, y).
Draw the line from this point to the centre. The angle between this line and the x axis, A, has the property
cos (A) = -0.2
i.e.
A = arccos (-0.2)
so sin (arccos(-0.2)) is just sin (A), and from the diagram this is just y.
You can just draw the diagram as described in the first paragraph and measure y. Or use Pythagoras''s theorem to calculate it: the rihgt angled triangle is the one with the radius of the circle as it''s hypotenuse, giving
y2 + (0.2)2 = 1
and so y = sqrt (1 - (0.2)2) = sqrt (0.96)
(and I would say this IS game related: using such non-trig methods to solve problems involving trig is a big win in games where trig is too slow and innacurate to be widely used. And this is perhaps the single most useful method to know).