text: Ok, this is a pretty easy question. FOLLOW ME WITH A PENCIL AND A PIECE OF PAPER OR THIS WILL BE CONFUSING!Here it is:\n1. RT is perpendicular to US   (Given)\n2. S is midpoint of RT (Given)\n3. Connect point U to R and U to T to form two side-by-side       triangles\n4. Now, angle UST is 90 degrees and USR is also 90 degrees(Def. of perpendicular lines)\n5. line ST is equal to line SR (Def. of midpoint) \n6. The two triangles share the same side line US. So, US is same to itself...\n7. Triangle USR is equal to UST (SAS Postulate)