beam
First you draw a square. A square has 4 right angles. If you draw a line above one of the right angles and rub out the angle which you have drawn a line above you have a pentagon with 3 right angles.
A line with equal angles from a surface is referred to as being normal
The word 'Triangle' is a collective noun for different shaped triangles. They are ;- Equilateral(Acute) ; all sides are the same length , and all angles are 60 degrees. Isosceles (Can be Obtuse) ; two sides are the same length and two angles are equal. Right-angles (only Acute) ; one of the angles is a right angle(90 degrees) Scalene ; All sides are different length and all angles are different values. May be either acute of obtuse. For ALL triangles, on a plane surface, the sum of the interior angles is ALWAYS 180 degrees. NB For triangles drawn on a 3-dimensional surface, ( a sphere ; the Earth) the angles may add to 360 degrees.
straight up or pointing to the zenith or in a direction at right angles to the surface of the earth
... right angles, by definition of a rectangle.... right angles, by definition of a rectangle.... right angles, by definition of a rectangle.... right angles, by definition of a rectangle.
a crack
a straight line
A Triangle drawn accross a sphere; NOT on a plane surface.
It is called "Lateral Inversion". Lateral means "sideways". The term is used because the image often seems left-right reversed. In fact the inversion is really at right angles to the mirror surface, but it can appear to be laterally reversed.
They are perpendicular lines
First you draw a square. A square has 4 right angles. If you draw a line above one of the right angles and rub out the angle which you have drawn a line above you have a pentagon with 3 right angles.
In Euclidean geometry, 180. Other answers are possible, depending on the surface on which the triangle is drawn.
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a regular
A line with equal angles from a surface is referred to as being normal
At the point where the rays meet at the mirror, draw a line at right angles to the mirror (normal means 90 degrees)
Yes, but not on a plane surface; only on a curved surface.