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First of all, this problem has nothing to do with Trigonometry. Please try to post your problems using a relevant category. You are more likely to get faster, better help when you post in an appropriate category.
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\n" ); document.write( "This is the equation of a circle. So we are looking to find an expression for the function that is the top half of the circle.
\n" ); document.write( "Functions are usually written in the form:
\n" ); document.write( "y = something
\n" ); document.write( "So we will start by trying to transform the equation into this form. First we subtract x squared:
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\n" ); document.write( "Next we will find the square root of each side. This is where it gets a little tricky. Every positive number has two square roots, a positive one and a negative one. So when we find the square root of each side we have to include both square roots. This is one reason we use the \"plus-or-minus\" sign:
\n" ); document.write( "y-4 = +
\n" ); document.write( "And last we add 4 to each side:
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\n" ); document.write( "This of course is the equation of the whole circle. For just the top half, do you think we should use the positive square root or the negative square root? Since the right side is an expression for a y value, I hope it makes sense that we should use the positive square root (since it will make the y value bigger). So the equation for the function that is the top half of the circle would be:
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\n" ); document.write( "And the equation for the function that is the bottom half would be:
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