# Chapter 17: Introducing Trigonometry

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## SOHCAHTOA 1 of 3

## Finding a Side

1. Label the sides of the triangle: hyp is opposite the right angle and opp is opposite the known angle

2. Identify whether sin, cos, or tan is appropriate for your problem. Use the formula that includes both your known side and wanted side. e.g. if you need to find the adjacent side of an angle, and know the opposite side, you would need to use tan.

3. Manipulate the formula to be useful. e.g. to find the adjacent side of the angle, the formula would become A = O / tan(angle)

4. Substitute the expressions for the numerical values. e.g. x = 12 / tan(25)

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## Finding an Angle

As with finding a side, use the before 4 steps, instead using inverse sin (sin-1), cos (cos-1) or tan (tan-1)

Tip: use brackets and round off to 3 sig figs after all calculations. Remember bearings:

North: 000
East: 090
South: 180
West: 270

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