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### TRIGONOMETRY

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ഀ ACTIVITY 1

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### Observations

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### Conclusions

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Trigonometry (from Greek trigōnonഀ
"triangle" + metron "measure") isഀ
a branch of mathematics that studies triangles and the relationships betweenഀ
their sides and the angles between these sides.

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Trigonometry defines the trigonometric functions, which describe thoseഀ
relationships. In mathematics, the trigonometric functions are functions of anഀ
angle. They are used to relate the angles of a triangle to the lengths.

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Ask learners to look around their environment and determine areas whereഀ
triangles have been used.

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There are an enormous number of uses of trigonometry. For instance it is usedഀ
in construction of buildings (windows, doors, roof truss), in astronomy toഀ
measure the distance to nearby stars, in geography to measure distances betweenഀ
landmarks.

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Sextants are used to measure the angle of the sun or stars with respect to theഀ
horizon. Using trigonometry and a marine chronometer, the position of the shipഀ
can be determined from such measurements.

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The hypotenuse is the side opposite to the 90 degree angle in a rightഀ triangle; it is the longest side of the triangle, and one of the two sidesഀ adjacent to angle B. The adjacent leg is the other side that is adjacent toഀ angle B. The opposite side is the side that is opposite to angle B. The termsഀ perpendicular and base are sometimes used for the opposite and adjacent sidesഀ respectively.

ഀ ഀഀ ACTIVITY 1

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1. Draw four different right angle triangles but having same angle θ = 40ഀ
degrees.

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Copy and complete the table below:

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2. Repeat the above activity with different triangles but θ = 50 degrees.

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Many English speakers find it easy to remember what sides of the rightഀ
triangle are equal to sine, cosine, or tangent, by memorizing the wordഀ
SOH-CAH-TOA.

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The first trigonometric table was apparently compiled by Hipparchus, who is nowഀ
consequently known as "the father of trigonometry".