G-CO.9
Prove theorems about lines and angles. Theorems include: vertical angles are congruent; when a transversal crosses parallel lines, alternate interior angles are congruent and corresponding angles are congruent; points on a perpendicular bisector of a line segment are exactly those equidistant from the segment’s endpoints.
Khan Academy ResourcesTriangle angles reviewFinding angle measures between intersecting linesFinding angle measures using trianglesFind angles in trianglesAngle relationships with parallel linesEquation practice with anglesEquation practice with angle additionFind angles in isosceles trianglesLine and angle proofsProofs with transformationsAngles, parallel lines, & transversalsAngles in a triangle sum to 180° proofWorked example: Triangle angles (intersecting lines)Worked example: Triangle angles (diagram) Triangle exterior angle exampleIsosceles & equilateral triangles problemsMeasures of angles formed by a transversalProofs with transformationsMissing angles with a transversal

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