Properties of plane figures
angles and parallel lines, angles in a parallelogram, angles in an isosceles triangle, the triangle inequality, angle sums in polygons, angles of regular polygons, triangle congruence, choosing the justification in a proof
Exercises are drawn at random from a large bank - every click gives a different set.
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Problem
An interior angle of a regular polygon is 108°. How many degrees is the exterior angle at the same vertex?
Problem
How many degrees is one interior angle of a regular triangle?
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Two triangles are such that the three sides of one are equal to the three sides of the other. Which congruence condition shows that they are congruent?
Problem
The angle between the equal sides of an isosceles triangle is 10 times each base angle. How many degrees is the angle between the equal sides?
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Statement: "Every triangle with an obtuse angle is isosceles." Which answer is a counterexample, that is, shows that the statement is false?
Problem
Two sides of a triangle are 4 cm and 2 cm long, and the third side is a whole number of centimetres. What is the largest possible perimeter of this triangle?
Problem
Lines k and l are parallel, and line m crosses both of them. One of the angles that line m makes with line k is 145°. How many degrees is the angle that makes a straight angle together with the corresponding angle at line l?
Problem
The interior angles of a polygon add up to 1260°. How many sides does it have?
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All the lines lie in one plane and are different. Line l is perpendicular to line n, and line q is parallel to line p. How do lines l and p lie relative to each other?
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The vertices of triangles ABC and KLM correspond like this: A to K, B to L, C to M. Which data are enough to show that these triangles are congruent?
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