2 Hypotenuse The longest side of a right angled triangle Always opposite the right angleHypotenuse
3 Pythagoras’ TheoremThe two smaller sides, squared and added together equals the hypotenuse squared.A2 + B2 = C2Only works for right angled triangles
4 Find the length of ‘j’ To find ‘j’, use P.T. Label the hypotenuse. j = 9 cm15cmhyp12cmj
5 Any other sort of questions? If it is then the hypotenuse is 6cm (longest side) and P.T. will work.= = 4162 = 36so = 62P.T. does NOT work so no right angleIs this triangle right- angled?Hyp?4cm6cm5cm
7 Don’t forget trigonometry. (Worth big marks) Unfortunately notDon’t forget trigonometry.(Worth big marks)
8 Key trigonometry facts Trigonometry links the size of the angles to the length of the sides.Only works in right angled triangles.Can be used to find either a length or an angleDon’t forget to check that your calculator is working in degrees.
9 Help! Label the sides of your triangle Hypotenuse (hyp) - opposite the right angle.Opposite (opp) - opposite the angle you know or want to find.Adjacent (adj) - the remaining side.
10 Then pick your equation. Sin 0 = opp Cos 0 = adj Tan 0 = opphyp hyp adj0 is the Greek letter ‘theta’ which denotes an angle.
11 But which one should I use? If you are trying to find an angle, work out which two sides you know and use the formula that contains them both.To find a missing side, work out which side you want to find and the side you know and then use the formula which contains both.
12 What?Find the value of ‘f’We know the hypotenuse and want to find ‘f’ which is the opposite.We use sin 300 = f / 1010 x sin 300 = ff = 5cm10cm‘f ’hypopp300adj
13 Find the value of angle BCA If I call angle BCA, ‘x’tan x = 4 / 10 = 0.4so x = tan-1 0.4x = 21.8o ( to 1 d.p.)A4cmhypoppBC10cmadj