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Grade 7Trigonometry

Angela measured the angle of elevation of a flagpole a and found out that it is 38 degree she then walked 25 metres towards the tree and measure the angle of elevation again to be 50° A. Sketch the diagram
B . Use the scale of 1 cm to represent 10 metres to draw the diagram accurately
C. Find the actual height of the tree
D. Find total distance of the bottom of the tree and initial position of Angela

Profile image of Erigo Senorina
5 Years agoGrade 7
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1 Answer

Profile image of Askiitians Tutor Team
ApprovedApproved Tutor Answer1 Year ago

To tackle this problem, we need to visualize the scenario and apply some trigonometric principles. Let’s break it down step by step, starting with the diagram and then moving on to the calculations.

Visual Representation

First, let’s sketch the situation. We have a flagpole and a tree, with Angela measuring angles of elevation from two different positions. Here’s how to represent it:

  • Position A: Angela's initial position, where she measures the angle of elevation to the flagpole at 38 degrees.
  • Position B: Angela walks 25 meters towards the tree and measures the angle of elevation to the flagpole again, now at 50 degrees.
  • Let’s denote the height of the flagpole as 'h' and the horizontal distance from Position A to the base of the flagpole as 'd'.

Scale Drawing

Using the scale of 1 cm to represent 10 meters, we can convert the distances into centimeters for our diagram:

  • Distance from Position A to the base of the flagpole (d) will be represented as d/10 cm.
  • Distance from Position B to the base of the flagpole will be (d - 25)/10 cm.

Now, let’s draw the diagram based on these distances and angles. The height of the flagpole can be represented using the tangent function from the angles of elevation:

Calculating Height of the Flagpole

From Position A, we can use the tangent of the angle of elevation:

tan(38°) = h / d

From Position B, we have:

tan(50°) = h / (d - 25)

Setting Up the Equations

Now we can express 'h' in terms of 'd' from both equations:

  • From Position A: h = d * tan(38°)
  • From Position B: h = (d - 25) * tan(50°)

Equating the Two Expressions for Height

Since both expressions equal 'h', we can set them equal to each other:

d * tan(38°) = (d - 25) * tan(50°)

Solving for 'd'

Now, let’s solve for 'd':

  • Expanding the right side: d * tan(38°) = d * tan(50°) - 25 * tan(50°
  • Rearranging gives: d * tan(38°) - d * tan(50° = -25 * tan(50°)
  • Factoring out 'd': d(tan(38°) - tan(50°) = -25 * tan(50°)
  • Thus, d = -25 * tan(50° / (tan(38°) - tan(50°))

Calculating 'd' Numerically

Using a calculator, we find:

  • tan(38°) ≈ 0.7813
  • tan(50°) ≈ 1.1918

Substituting these values into the equation:

d ≈ -25 * 1.1918 / (0.7813 - 1.1918)

Calculating this gives us:

d ≈ 25 * 1.1918 / 0.4105 ≈ 72.5 meters

Finding the Height of the Flagpole

Now that we have 'd', we can find the height 'h':

h = d * tan(38°) ≈ 72.5 * 0.7813 ≈ 56.7 meters

Calculating Total Distance from Angela's Initial Position to the Tree

Angela walked 25 meters towards the tree, so the total distance from her initial position to the base of the tree is:

Total Distance = d + 25 ≈ 72.5 + 25 = 97.5 meters

Summary of Results

In summary:

  • The height of the flagpole is approximately 56.7 meters.
  • The total distance from Angela's initial position to the base of the tree is approximately 97.5 meters.

This approach combines trigonometric principles with a clear understanding of the scenario, allowing us to find the required measurements effectively. If you have any further questions or need clarification on any part, feel free to ask!