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

[Tlark10]

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

 

[tommyxu3]

Just let $x=\cos \theta.$ Then by $\sin^2 \theta+\cos^2 \theta =1,$ you can get what you want.

 

[Nipuna Weerasekara]

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).