## -:Triangles:-

**(Basic-Propotionality Theorem) OR (Thale's Theorem)**

Two triangles are similar, if

1.their corresponding angles are equal and

2.their corresponding sides are proportional

## -: Trigonometry:-

#### Trigonometric-Ratios of 0°,30°,45°,60°,90°

#### Trigonometric-Ratios of Complementary Angles

## -: Coordinate Geometry:-

#### Distance Formula

#### Section Formula

#### Midpoint Formula

**Centroid of a Triangle**

## -: Circles:-

Theorems :

## -:Area Related to Circles:-

### Formulae on Area of circle, sector and segments

## -: Surface Area and Volume:-

## -:Statistics & Probability:-

Three measures of central tendency are useful for analysing the data, namely

(a) Mean

(b) Median

(c) Mode

### Mean of Grouped data

To calculate the mean of grouped data, we have following three methods

- Direct method
- Assumed mean method
- Step deviation method

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