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C 2 1. sin A 5 2. cos A 21 5 2 2 21 3. tan A 21 21 5 A 2 M 4. If C = 20º, then cos C is equal to: A. sin 70 B. cos 70 C. tan 70 Skills Check CCGPS Geometry Day 39 (10-3-14) UNIT QUESTION: What patterns can I find in right triangles? Standard: MCC9-12.G.SRT.6-8 Today’s Question: How do we use trig ratios to find the missing sides and angles of a triangle? Standard: MCC9-12.G.SRT.6-8 Using Trig to Find Missing Angles and Missing Sides Finding a missing angle. (Figuring out which ratio to use and an inverse trig button.) Ex: 1 Figure out which ratio to use. Find x. Round to the nearest tenth. O 20 tan 20 m 40 1 20 tan x 40 26.6 o A 40 m x Shrink yourself down and stand where the angle is. Identify the given sides as H, O, or A. What trig ratio is this? Ex: 2 Figure out which ratio to use. Find x. Round to the nearest tenth. O 15 sin 15 m 50 1 15 sin x 50 17.5 o H 50 m x Shrink yourself down and stand where the angle is. Identify the given sides as H, O, or A. What trig ratio is this? Ex. 3: Find . Round to the nearest degree. 17.2 tan 9 O 17.2 9 A 17.2 tan 9 1 62 Ex. 4: Find . Round to the nearest degree. A 7 23 H 7 cos 23 7 cos 23 1 72 Ex. 5: Find . Round to the nearest degree. 200 O H 200 sin 400 200 sin 400 1 30 Finding a missing side. (Figuring out which ratio to use and getting to use a trig button.) Ex: 6 Figure out which ratio to use. Find x. Round to the nearest tenth. x tan 55 20 20 m 55 A 20 tan 55 x x 28.6 m O x Ex: 7 Find the missing side. Round to the nearest tenth. O 80 ft 72 x A 80 tan 72 x x tan 72 80 80 x tan 72 x 26 ft Ex: 8 Find the missing side. Round to the nearest tenth. x O H 283 m 24 x sin 24 283 283sin 24 x x 115.1 m Ex: 9 Find the missing side. Round to the nearest tenth. H 20 ft 40 x A x cos40 20 20 cos40 x x 15.3 ft When we are trying to find a side we use sin, cos, or tan. When we are trying to find an angle we use (INVERSE) -1 -1 -1 sin , cos , or tan .