geometry - definitions

Question 1

intersecting

Answer 1

they have a common point

Question 2

paralell

Answer 2

they lie on one plane and have no point in common

Question 3

skew

Answer 3

they’re not intersecting and not parallel

Question 4

complementary angles

Answer 4

when we add two angles together it equals 90

Question 5

supplementary angles

Answer 5

when we add two angles together it equals 180

Question 6

theorem

Answer 6

the sum of the interior angles of a triangle is 180
the sum of the exterior angles is 360

Question 7

right tringle

Answer 7

1 right, 2 acute angles

Question 8

acute triangle

Answer 8

3 acute angles

Question 9

scalene triangle

Answer 9

no equal sides and angles

Question 10

isosceles triangle

Answer 10

same legs

Question 11

equilateral/regular triangle

Answer 11

equal sides and angles

Question 12

medians

Answer 12

medians connect a vertex with the opposite side’s midpoint
intersect each other in one central point
the centroid divides the triangle into 1:2 parts
the median divides the area of the triangle in half
6 small triangles with the same areas

Question 13

angle bisectors

Answer 13

cuts the angles into 2 equal parts
they intersect each other in 1 point, this point is the centre of the inscribed angle

Question 14

perpendicular bisectors

Answer 14

cuts the sides into 2 equal parts
intersection: centre of the circumscribed circle

Question 15

altitudes

Answer 15

drawn from the vertex to the opposite side so that it’s perpendicular to the side
intersection ortocentre

Question 16

midlines

Answer 16

the midline connects 2 midpoints of 2 different sides
every midline is parallel to the third side and its length is half

Question 17

pythagorean theorem

Answer 17

in a right angled triangle the sum of the squares of the legs is equal to the square of the hypotenuse

Question 18

triangle inequality

Answer 18

the sum of two sides is greater than the length of the third side