Revision Notes – Triangles
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Types of Triangles |
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Equilateral |
Isosceles |
Scalene |
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three equal sides three equal angles each angle is 60º
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two
sides equal
base angles equal
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3
unequal sides
3 unequal angles
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Facts about Triangles |
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| The three angles in
a triangle add up to 180º
A + B + C = 180º |
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| The exterior angle in a
triangle is equal to the sum of the two interior opposite
angles.
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| In a triangle, the biggest angle is always opposite the longest side and the smallest angle is always opposite the shortest side. |
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| In a right angled triangle, the
side opposite the right angle is called the hypotenuse. The
hypotenuse is always the longest side.
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Congruent Triangles |
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| Two shapes are congruent if they
have the exact same size and shape
Triangles are congruent if one of the following rules apply. The sign for congruency is ≡ |
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SSS (side, side, side) |
Three sides of one triangle = three sides of other triangle |
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SAS (side, angle, side) |
Two sides and the included angle in one triangle = two sides and included angle in other triangle |
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ASA (angle, side, angle) |
One side and two angles of one triangle = one side and two angles in other triangle |
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RHS (right angle, hypotenuse, side) |
A right angle, the hypotenuse and another side of one triangle = a right angle, the hypotenuse and another side of one triangle |
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