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coordinates and trigonometry

I have to find the coordinates for S(i).

My attempt :

OP = 1 * 1/2 = 1/2

(1/2)^{2} + x^{2 }= 1^{2}

x = √(3)/2

cos^{-1}(√(3)/2) = 30

sin^{-1}(1/2) = 30

t = 30

cos(2*t) = cos(60) = 1/2

sin(2*t) = sin(60) =√(3)/2

S(i) = (1,2 , √(3)/2 )

Re: coordinates and trigonometry

t is not 30°. t is arctan(1/2). And so your coordinates (cos(2t),sin(2t)) = ?

Re: coordinates and trigonometry

Can you try to explain why t= arctan(1/2) because I can't see it.

And can't I use arccos and arcsin instead of arctan?

Re: coordinates and trigonometry

The angle of inclination of a line having slope is .

.

Now, use the double-angle identities for sine and cosine and:

Re: coordinates and trigonometry