Pythogoras theorem :
In a right- angled triangle, the square of hypotenuse is sum of the squares of the base and the perpendicular.
The ratios of the sides of a right-angled triangle with respect to its angles are called trigonometric ratios.
Trigonometric Ratios of certain Angles
Trigonometric Ratio of 30°
Note : if in a right- angled triangle, one angle is 30°, then the side opposite to it is half of the hypotenuse.