🚀 go-pugleaf

This is a good page.

Concentrate on practical applications involving triangles.

If you know 3 things about a triangle, at least one thing being the length
of a side, all the other things you wish to know about the triangle can be
calculated using trigonometry. It is known as Solving The Triangle.

Trigonometric ratios such Sine, Cosine, Tangent are related ONLY to
right-angle triangles. One of the angles must be a right-angle, ie, 90
degrees. These three ratios of the lengths of sides are the only ones you
really need.

The same triangles can be solved by Geometry using a ruler, protractor and
pencil and paper, as did the ancient Greeks. When you have a trigonometric
problem always make a little sketch of the triangle on paper. You will then
see very clearly what the problem is about.  But trigonometry is far more
accurate and involves not much more than arithmetic..

The slant distance to the top of a mountain is 10 kilometres. The elevation
angle is 30 degrees. (The 3rd thing which is known is that one angle is 90
degrees.) How high is the mountain ? This is a very practical problem
because it is impossible to measure the height directly. When you can solve
this you can solve them all.
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Reg