**Pythagoras Theoram:**

For all the right angled triangles “the square on the hypotenuse (c^{2}) is equal to the sum of all the squares on the other two sides (a^{2} + b^{2 }).

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

**Trigonometrical Ratios of Acute Angle:**

All angles in a right angle triangle are acute angles. (between 0 to 90 degrees).

**Sine:**

**Cosine:**

**Tangent:**

*Tip to remember this SOH CAH TOA.*

**Example:**

Q: Find the unknown values of :

Sin 30 = Opposite / Hypotenuse

Sin 30 = x / 13

X = 6.5 Ans

Y^{2} + X^{2} = 10^{2}

Y^{2 }= 10^{2 }– 6.5^{2}

Y = 7.60 (Ans)

**Trigonometrical Ratios of Obtuse Angles:**

The trigonometric ratios of an obtuse angle (between 90 and 180 degree) can be expressed in terms of the adjacent acute angle that lies in the same straight line.

**Area of Triangle:**

For a known right angled triangle with any two sides given and the area.

Area = ½ ab sin C

Area = ½ bc sin A

Area = ½ ac sin B

**Sine Rule: **

It can be used when:

- Two angles and one side given.
- Two sides and one non-included angle given.

**Cosine Rule:**

a^{2=} b^{2 }= c^{2} – (2bc cos A)

b^{2=} a^{2 }= c^{2} – (2ac cos B)

c^{2=} a^{2 }= b^{2} – (2ab cos C)

It can be used when:

- Three sides are given.
- Two sides and one angle is given.