Expression 6: "x" squared plus "y" squared equals "r" squared left brace, "y" greater than or equal to 0 , right brace Has graph. To audio trace, press ALT+T.x2+y2=r2y≥0
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Expression 7: "y" equals tangent left parenthesis, alpha , right parenthesis "x" left brace, "y" greater than or equal to 0 , right brace Has graph. To audio trace, press ALT+T.y=tanαxy≥0
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Hidden Label: left parenthesis, "r" cos left parenthesis, alpha , right parenthesis , "r" sin left parenthesis, alpha , right parenthesis , right parenthesisrcosα,rsinα