document.write( "Question 133828: PROVE: ST is perpendicular to SY.
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\n" ); document.write( "Angle 1 is Congruent to Angle 2;
\n" ); document.write( "PQ is Perpendicular to SY\r
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\n" ); document.write( "PLEASE PLEASE HELP! \n" ); document.write( "
Algebra.Com's Answer #97926 by Edwin McCravy(20060)\"\" \"About 
You can put this solution on YOUR website!
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document.write( "(Note: We have to assume PXT is a straight line segment or else it\r\n" );
document.write( "couldn't be true.)\r\n" );
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document.write( "PLAN:\r\n" );
document.write( "We only have to prove that all three triangles in the \r\n" );
document.write( "figure are right triangles which have their corresponding angles\r\n" );
document.write( "congruent.  For then Angle S will be congruent to right Angles \r\n" );
document.write( "4 and 5. \r\n" );
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document.write( "The \"main\" theorem we will use is:\r\n" );
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document.write( "If two angles of a triangle are congruent to two angles\r\n" );
document.write( "of another triangle, then the third angles are also congruent.\r\n" );
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document.write( "Angles 4 and 5 are given as right angles and Angle 1 is \r\n" );
document.write( "Congruent to Angle 2.  Therefore by that \"main\" theorem above,\r\n" );
document.write( "Angles P and Y are congruent.\r\n" );
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document.write( "Therefore Angle P and Angle T are congruent, for they are both\r\n" );
document.write( "congruent to Angle Y.\r\n" );
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document.write( "Angles 1 and 3 are congruent because they are vertical angles.\r\n" );
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document.write( "Therefore by the \"main\" theorem above, Angles 4 and S are\r\n" );
document.write( "congruent. \r\n" );
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document.write( "Angle 4 is a right angle.\r\n" );
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document.write( "Therefore Angle S is also a right angle, and that proves that\r\n" );
document.write( "ST is perpendicular to SY.\r\n" );
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document.write( "Edwin
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