Programmers mathematics (28) - an acute angle trigonometric functions

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concept

As shown in the right-angled triangle ABC.

The ratio of the hypotenuse side is called acute angle A of ∠A 正弦, denoted sin A, namely:
$\ That \; A = \ frac {BC} {AC}$

Similarly, the ratio of the hypotenuse limb, called 余弦, denoted by cosA, namely:

$\ Cos \; A = \ {AB} {freely AM}$

And the ratio of the side limb, called 正切, denoted by tan A, namely:

$\tan\;A=\frac{BC}{AB}$

Sine, cosine, tangent are ∠A of 锐角三角函数.

Solution right triangle

When determined acute angle, sine, cosine, tangent have been identified, so we can easily measured by a length, the other is not easy to calculate the length of the calculation.

E.g:

The trigonometric function tan A = BC / AB.
I.e. tan38 = BC / 100.
BC = 100 * tan38.
This time to come up with a calculator, you can obtain a high degree of BC.