So I've been working very hard on my trigonometry on khan academy. However I'm constantly getting stumped by one type of question in particular.
There is some fundamental flaw in my understanding.
I know what the unit circle is completely and why $\sin{\theta} = y$, however, in the following question I completely DO NOT understand why the answer wasn't B and G. The answer apparently was only G!
Why Isn't the y co-ordinate of $B = \sin{\theta}$ ?
Answer
The line segment $OG$ is at an angle of $\theta$ from the positive $x$-axis, whilst the line segment $OB$ is at an angle of $\theta$ from the negative $x$-axis and hence an angle of $\pi + \theta$ from the positive $x$-axis, so that the $y$-coordinate of $B$ is $\sin(\pi + \theta) = -\sin(\theta)$.
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