Don't understand how eqn 2 was reached from eqn 1.

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Tlark10
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moved from general forum so homework template is missing
I have found solutions to a question I am trying to figure out, and I am unsure how they got from one step to the next. Is it some sort of integration??

Eqn 1) 0.625 = sin(theta) - 0.5cos(theta)

Eqn 2) 0.625 = sqrt(1 - x^2) - 0.5x
 
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Just let ##x=\cos \theta.## Then by ##\sin^2 \theta+\cos^2 \theta =1,## you can get what you want.
 
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tommyxu3 said:
Just let ##x=\cos \theta.## Then by ##\sin^2 \theta+\cos^2 \theta =1,## you can get what you want.
I second this. Next time just look at the two equations and try to see any resemblance. Then you might find some. In here you might see x=Cos(theta) directly whereas you might see Sin(theta)= SqRt(1-x^2).