World 5-1 Trigonometric Ratios Recall that in the past finding an unknown side of a right triangle required the use of Pythagoras theorem. By using trig ratios we can now solve unknown sides of a triangle and determine all the angles. No more Pythag! Eg.1- First we must label the sides properly Adjacent Opposite Hypotenuse Opposite Adjacent Hypotenuse The adjacent side always touches the angle. Eg. 2 To remember the trig ratio formulas think SOHCAHTOA sin opp hyp cos adj hyp tan opp adj theta is used to represent the angle in degrees Eg. 3 Calculate to 3 decimal places a) sin 27 o = b) cos 56 o = c) tan 78 o = d) sin 90 o = e) tan 20 o = f) sin 62 o = What cos60 o tells us is that if the angle is 60 degrees the ratio of the length of the adjacent over the hyp is o opp adj hyp 60 o opp hyp adj To determine the unknown angle press sin -1, cos -1, or tan -1 Eg. 4 Calculate the angle to 1 decimal place a) sin = 1/2 b) cos = 0.3 c) tan = 8.1 d) sin = 1 e) tan = 0.43 f) sin = o 72.5 o 83 o 90 o 23.3 o 45.2 o Eg. 5 Determine unknown measure d) Homework World 5-1 Handout