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©1998 ThinkQuest
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©1998 ThinkQuest
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Trigonometry
Trigonometry is an advanced math topic. It is also the most widely used advanced math topic. Many fields including scientific research and ocean navigation require the knowledge of trigonometry. Trigonometry is fairly easy once you firmly know the basics, and key to do well on trigonometry is memorization. There are a great of deal of formulas and values that are needed to be well memorized.
The concept of trigonometry is based on right triangle. There are three values in a right triangle. They are the lengths of the two legs and the hypotenuse. Trigonometry also has three basic values. They are called sine (sin), cosine (cos), and tangent (tan). These three values are the values of the non-right angles of the right triangle. The sin value of a non-right angle of a right triangle is equal to the length of the side opposite to the angle divided by the hypotenuse. The cos value of a non-right angle of a right triangle is equal to the length of the side adjacent to the angle divided by the hypotenuse. The tan value of a non-right angle of a right triangle is equal to the length of the side opposite to the angle divided by the length of the side adjacent to the angle. These three values are very important part of trigonometry and should be committed to memory.
Until now we have only approach trigonometry from the right triangle point of view or triangular trigonometry, which can only cover the angles up to 90 degrees, but what about the angles over 90 degrees? How are we going to find the sin, cos, and tan values of the angles greater than 90 degrees? The answer is the circle or circular trigonometry. We start with a concept called the unit circle. A unit circle is a circle with radius of one, and therefore it has area of P and circumference of 2P . We divide the circle into twelve parts with twelve points. So the first point is P /6; second point is P /3; third point is P /2 and so on. The last point or the starting point is 2P because the circle has just completed
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