**What is meant by trigonometry? Give some important trigonometric ratios.**

Difficulty: Easy

**Trigonometry:**

Trigonometry is a branch of mathematics that deals with the properties of a right-angled triangle.

**Trigonometric ratios:**

Consider a right-angled triangle $\triangle ABC$ having $\theta$ at A.

$\sin \theta$ = Perpendicular/ Hypotenuse $\frac{BC}{AB}$

$\cos \theta$ = Base/Hypotenuse $\frac{AC}{AB}$

$\tan \theta$ = Perpendicular/Base = $\frac{BC}{AC}$

**Note:**

To remember trigonometric ratios, we use the following sentence:

“Some people have – Curly brown hair – Through proper brushing”

**Pythagoras theorem:**

$\left(Hypotenuse\right)^{2}=\left(Base\right)^{2}+\left(Perpendicular\right)^{2}$

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