In ( \triangle ABC ), ( AB=5, BC=7, AC=9 ). Which angle is largest? Largest side ( AC ) → opposite ( \angle B ) is largest. 7. Hinge Theorem (SAS Inequality) If two sides of one triangle are congruent to two sides of another, and the included angle of the first is larger, then the third side of the first is longer.
Triangle ( ABC ) has midpoints ( D ) on ( AB ) and ( E ) on ( AC ). If ( BC = 18 ), find ( DE ). Answer: ( DE = 9 ) 2. Perpendicular Bisectors & Circumcenter Perpendicular bisector: A line/segment/ray perpendicular to a segment at its midpoint. unit 5 test study guide relationships in triangles
Can sides 4, 7, 12 form a triangle? ( 4+7 = 11 \not> 12 ) → No. Angle-Side Relationship: Largest angle opposite largest side, smallest angle opposite smallest side. In ( \triangle ABC ), ( AB=5, BC=7, AC=9 )
If third sides differ, the angle opposite the longer side is larger. If ( BC = 18 ), find ( DE )
In ( \triangle ABC ), median ( AD ) has ( AG = 8 ). Find ( GD ). ( \fracAGGD = \frac21 ) → ( 8/GD = 2 ) → ( GD = 4 ) 5. Altitudes & Orthocenter Altitude: Perpendicular segment from vertex to opposite side (or extension).
Triangles ( ABC ) and ( DEF ) have ( AB=DE, AC=DF ), ( \angle A=80^\circ, \angle D=60^\circ ). Compare ( BC ) and ( EF ). ( BC > EF ) 8. Exterior Angle Theorem Exterior angle = sum of two remote interior angles.
I’ll organize it by , theorems , formulas , and example problem types you’ll likely see on the test. 1. Midsegments of a Triangle Definition: A segment connecting the midpoints of two sides of a triangle.