2. The Beginning of Trigonometry Trigonometry can be used to calculate the lengths of sides and sizes of angles in right-angled triangles. The three formulas: sin, cos, tan The sides of the right-angled triangles are given special names - the hypotenuse, the opposite and the adjacent. The hypotenuse is the longest side and is always opposite the right angle. The opposite and adjacent sides relate to the angle under consideration. There are three formulae involved in trigonometry: sin = opposite / hypotenuse cos = adjacent / hypotenuse tan = opposite / adjacent Which formula you use will depend on the information given in the question. There are a couple of ways to help you remember which formula to use. Remember SOHCAHTOA (it sounds like 'Sockatoa') or Some Old Hag Cracked All Her Teeth On Apples.

3. Cont. SOH- S means sin CAH- C means cos TOA- T means tan O means opposite A means adjacent O means opposite H means hypotenuse H means hypotenuse A means adjacent Make sure you follow this diagram above. ^^^^

4. Example We are given angle A and side AB. AB is the hypotenuse. BC is opposite angle A. Therefore we use the formula: sin = opposite / hypotenuse sin 30 = BC / 7 Multiply both sides by 7 7 x sin30 = BC Using a calculator we get BC = 3.5cm

5. Practice Questions 1 2 3

6. ANSWERS: 1.4.77cm 2.5.52cm 3.7.15cm WELL DONE IF YOU GOT THEM ALL RIGHT!

7. Do you think trigonometry is easy now? I hope you do because we understand it. If you have any trouble with trigonometry still just ask us, Nitisha or Robyn. Trigonometry can be fun!