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Grade 10 Math · Problem type
Why a triangle’s angles add to 180°
Use this for “Prove that the angles of a triangle add to 180°.”
Put in order
Put the proof in order.
1
?
2
?
3
?
Assumptions
•
Through a point not on a line there is exactly one parallel line (the Parallel Postulate).
•
Parallel lines make alternate interior angles congruent.
•
Angles that make a straight line add to 180°.
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A perpendicular line through a point
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Rigid motions, compositions and symmetry
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Related lessons
Parallel and perpendicular lines: transversals and proofs
Main lesson
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Are the lines parallel?
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Angle expressions
Use this for “ℓ ∥ m, corresponding angles are (4x + 12)° and (2x + 50)°. Find x and the angle.”
A parallel line through a point
Use this for “Write the equation of the line parallel to y = 3x − 4 through (2, 7).”
A perpendicular line through a point
Use this for “Write the equation of the line perpendicular to y = 2x + 1 through (4, 3).”