# Geometry Symbols

Geometry (Ancient Greek: geo- "earth", -metria "measurement") is a branch of mathematics concerned with questions of shape, size, relative position of figures, and the properties of space. It is one of the oldest mathematical sciences. Initially a body of practical knowledge concerning lengths, areas, and volumes, in the 3rd century BC, Geo-metry was put into an axiomatic form by Euclid, whose treatment—Euclidean geo-metry—set a standard for many centuries to follow. Archimedes developed ingenious techniques for calculating areas and volumes, in many ways anticipating modern integral calculus. The field of astronomy, especially mapping the positions of the stars and planets on the celestial sphere and describing the relationship between movements of celestial bodies, served as an important source of geometric problems during the next one and a half millennia. A mathematician who works in this field is called a geo-meter.
Note : During the proofs in geometry congruence of triangle, if we mark the same sign on sides of two different triangles that means that two sides are congruent with each other.Similarly, if the same sign on angles of two different triangles or same triangles then that two angles are congruent to each other.
 Symbol Symbol Name Meaning/Definition Example 1) ∠ Angle formed by two rays ∠ABC = 60o 2) ⊾ Right angle 90o α = 90o 3) ≅ Congruent to Equivalence of geometric shapes and size ΔABC ≅ ΔPQR 4) ⊥ Perpendicular Perpendicular lines (90o angle) PQ ⊥ PR 5) Δ Triangle Triangle shape ΔABC = ΔXYZ 6) → Ray Line that start from point. 7) o Degree. 1trun = 360o α = 60o 8) π pi constant π= 3.141592654...is the ratio between the circumference and diameter of a circle. d = 2 πr 9) ∥ Parallel Parallel lines AB ∥ PQ 10) ∢ Spherical angle ∢ ABC = 30o

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