Mammoth Memory

Trigonometry – Sin Cos Tan


Trigonometry – is the relationship between the sides and angles of triangles.


An easy way to learn about this relationship is to remember:

Mnemonic to remember the formulas sin cos and tan in trigonometry

Sohcahtoa the great Native American war chief was very trigger-happy (trigonometry).


And then you can write down:


Pronounce          So – as in so what

                             Ca – as in cat

                           Toa – rhymes with boa (the snake)


In any right-angled triangle (90°), if we know:

i) The length of 2 sides


ii) One side and an angle


We can work out the lengths and angles of all the other elements in the triangle.

Trigonometry can be used to measure heights of large objects

This allows us to find the height of statues, trees or buildings.

Trigonometry can be used to measure distances or islands

This can be used to find the distances to islands.

We use one of three formulae to work this out:

`sin\ theta= (O)/H`

`cos\ theta= (A)/H`


`tan\ theta= (O)/A`

SOH stands for “Sine of an angle is Opposite over Hypotenuse”.

CAH stands for “Cosine of an angle is Adjacent over Hypotenuse”.

TOA stands for “Tangent of an angle is Opposite over Adjacent”.


Sin, cos and tan are abbreviations of sine, cosine and tangent, while `theta`  is the symbol used for an unknown angle, and is known as theta.

`sin\ theta= (Opposite)/(Hypoten\use)`

`cos\ theta= (Adjacent)/(Hypoten\use)`

`tan\ theta= (Opposite)/(Adjacent)`


These formulae can only be used in a right-angled triangle as below:

Sin cos and tan can only be used on right angle triangles

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