# Consider the following figure. Find the exact value of {eq}cos(A^{\circ}) {/eq}.

## Question:

Consider the following figure. Find the exact value of {eq}cos(A^{\circ}) {/eq}.

## A Brief History of Trigonometry

Many historical civilisations independently came up with different ideas and applications for the modern-day field of trigonometry. For example, Egyptians needed very accurate calculations in order to construct their pyramids. The modern field of trigonometry began in the greek civilisation. One of the earliest known tables of trigonometric functions was calculated by the Greek mathematician Hipparchus.

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The cosine of an angle in a right-angled triangle is given by dividing the length of the base of the angle to the hypotenuse of the triangle. Here,...