# Properties of Triangles

### Pythagoras Theorem

### a^{2} + b^{2} = c^{2}

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

### Cosine Law

### c^{2} = a^{2} + b^{2} - 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

### a^{2} = b^{2}+ c^{2} - 2bc (Cos A)

and

### b^{2} = c^{2} + a^{2} - 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