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Copyright © Pearson Australia (a division of Pearson Australia Group Pty Ltd) Trigonometry Angles of elevation and depression

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Elevation Depression Copyright © Pearson Australia (a division of Pearson Australia Group Pty Ltd) Next slide Previous slide easy medium Rules Examples hard Alternate angles harder Instructions for use n There are 5 worked examples shown in this PowerPoint plus explanations. n A red dot will appear top right of screen to proceed to the next slide. Click on either the navigation buttons or use the cursor keys to access the relevant slides.

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Elevation Depression Copyright © Pearson Australia (a division of Pearson Australia Group Pty Ltd) Next slide Previous slide easy medium Rules Examples hard Alternate angles harder Angle of elevation x The angle of elevation is the angle formed by the line of sight and the horizontal

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Elevation Depression Copyright © Pearson Australia (a division of Pearson Australia Group Pty Ltd) Next slide Previous slide easy medium Rules Examples hard Alternate angles harder Angle of depression x The angle of depression is the angle formed by the line of sight and the horizontal

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Elevation Depression Copyright © Pearson Australia (a division of Pearson Australia Group Pty Ltd) Next slide Previous slide easy medium Rules Examples hard Alternate angles harder Combining the two x x elevation depression It’s alternate angles all over again!

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Elevation Depression Copyright © Pearson Australia (a division of Pearson Australia Group Pty Ltd) Next slide Previous slide easy medium Rules Examples hard Alternate angles harder B A 21 h m Example 1 The angle of elevation of building A to building B is 25 0. The distance between the buildings is 21 metres. Calculate how much taller Building B is than building A. Step 1: Draw a right angled triangle with the given information. Step 3: Set up the trig equation. Angle of elevation Step 4: Solve the trig equation. 25 0 Step 2: Take care with placement of the angle of elevation

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Elevation Depression Copyright © Pearson Australia (a division of Pearson Australia Group Pty Ltd) Next slide Previous slide easy medium Rules Examples hard Alternate angles harder Step 1: Draw a right angled triangle with the given information. Step 3: Decide which trig ratio to use. 60 m 80 m Step 4: Use calculator to find the value of the unknown. A boat is 60 metres out to sea. Madge is standing on a cliff 80 metres high. What is the angle of depression from the top of the cliff to the boat? Step 2: Use your knowledge of alternate angles to place inside the triangle. Example 2 Angle of depression

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Elevation Depression Copyright © Pearson Australia (a division of Pearson Australia Group Pty Ltd) Next slide Previous slide easy medium Rules Examples hard Alternate angles harder Step 1: Draw a right angled triangle with the given information. Step 3: Decide which trig ratio to use. Step 4: Use calculator to find the value of the unknown. Step 2: Use your knowledge of alternate angles to place 20 0 inside the triangle. (nearest km) Example 3 Marty is standing on level ground when he sees a plane directly overhead. The angle of elevation of the plane after it has travelled 25 km is 20 0. Calculate the altitude of the plane at this time. 20 0 h 25 km 20 0 Plane Angle of elevation

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Elevation Depression Copyright © Pearson Australia (a division of Pearson Australia Group Pty Ltd) Next slide Previous slide easy medium Rules Examples hard Alternate angles harder Example 4 Kate and Petra are on opposite sides of a tree. The angle of elevation to the top of the tree from Kate is 45 o and from Petra is 65 o. If the tree is 5 m tall, who is closer to the tree, Kate or Petra? K P 45 0 65 0 5m k p Step 1: Draw a diagram Step 2: Set up the trig equations in two parts. KatePetra Step 3: Solve the equations and answer the question. Therefore, Petra is closer to the tree, since the distance is shorter. Answer

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Elevation Depression Copyright © Pearson Australia (a division of Pearson Australia Group Pty Ltd) Next slide Previous slide easy medium Rules Examples hard Alternate angles harder Example 5 Maryann is peering outside her window. From her window she sees her car and a bird hovering above her car. The angle of depression of Maryann’s car is 20 0 whilst the angle of elevation to the bird is 40 0. If Maryann’s window is 2m off the ground, what is the bird’s altitude at that moment? Step 1: Draw a diagramStep 2: Set up the trig equations in two parts. Find d first, then b. Step 3: Solve the equations and answer the question. Bird Car 40 0 20 0 2 m b d Therefore, The bird is 10.1m (5.5 + 4.6) from the ground at that moment.

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Elevation Depression Copyright © Pearson Australia (a division of Pearson Australia Group Pty Ltd) Next slide Previous slide easy medium Rules Examples hard Alternate angles harder Last slide Use the navigation buttons to repeat selected slides

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