Properties of Triangles

Pythagoras Theorem

a2 + b2 = c2

Where: c is the hypotenuse of a right angle triangle and a and b are two sides containing the right angle.

Cosine Law

c2 = a2 + b2 - 2ab (Cos C)

This formula is applicable to any triangle. Here a, b and c are the three sides of the triangle and A, B and C are the angle opposite to these sides respectively

similarly

a2 = b2+ c2 - 2bc (Cos A)

and

b2 = c2 + a2 - 2ca (Cos B)

Note: This is a general law and if you make any of the angles equal to 90 degrees it gives the Pythagoras Theorem as Cos of 90 degrees = 0

Sine Law

(Sin A)/a = (Sin B)/b = (Sin C)/c

This formula is applicable to any triangle. Here a, b and c are the three sides of the triangle and A, B and C are the angle opposite to these sides respectively

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