Triangle Area Using Trigonometry Practice Problems

Master calculating triangle area with trigonometry formulas through step-by-step practice problems. Perfect for geometry students learning sin, cos, tan applications.

📚Master Triangle Area Calculations with Trigonometry
  • Apply the formula Area = (1/2)ab sin(C) to find triangle areas
  • Calculate areas using two sides and included angle measurements
  • Work with degrees and radians in trigonometric area calculations
  • Solve real-world problems involving triangle area using trigonometry
  • Practice with right triangles, isosceles triangles, and scalene triangles
  • Convert between different angle measurements for accurate calculations

Understanding Area of a Triangle

Complete explanation with examples

How to calculate the area of a triangle using trigonometry?

Throughout geometry studies, which deal with various structures and shapes, you are required to calculate areas and perimeters. Each shape or structure has a different formula through which you can answer the question and calculate the area. Fortunately, there is one formula that can be applied to all triangles, and it can be used to calculate the area of a triangle using trigonometry.

In the field of mathematics, emphasis is also placed on trigonometry, which deals with the study of triangles, their angles, and sides. Every student is required to demonstrate knowledge of triangles (from right triangles to isosceles triangles), and thus also answer the question of how to calculate the area of a triangle using trigonometry.

One formula for all different triangles

Now that you know the formula for calculating the area of a triangle using trigonometry, you can use it in any question where you need to calculate areas in triangles. The formula for calculating the triangle:

Diagram of a triangle labeled ABC with sides AB = 5, AC = 8, and angle Y = 60°. The area formula  𝑆 𝐴𝐵𝐶 = (𝐴𝐵⋅𝐴𝐶⋅sin𝛾)/2 is shown.

Detailed explanation

Practice Area of a Triangle

Test your knowledge with 27 quizzes

Calculate the area of the triangle using the data in the figure below.

444777AAABBBCCC8.06

Examples with solutions for Area of a Triangle

Step-by-step solutions included
Exercise #1

Calculate the area of the right triangle below:

101010666888AAACCCBBB

Step-by-Step Solution

Due to the fact that AB is perpendicular to BC and forms a 90-degree angle,

it can be argued that AB is the height of the triangle.

Hence we can calculate the area as follows:

AB×BC2=8×62=482=24 \frac{AB\times BC}{2}=\frac{8\times6}{2}=\frac{48}{2}=24

Answer:

24 cm²

Video Solution
Exercise #2

Calculate the area of the triangle ABC using the data in the figure.

121212888999AAABBBCCCDDD

Step-by-Step Solution

First, let's remember the formula for the area of a triangle:

(the side * the height that descends to the side) /2

 

In the question, we have three pieces of data, but one of them is redundant!

We only have one height, the line that forms a 90-degree angle - AD,

The side to which the height descends is CB,

Therefore, we can use them in our calculation:

CB×AD2 \frac{CB\times AD}{2}

8×92=722=36 \frac{8\times9}{2}=\frac{72}{2}=36

Answer:

36 cm²

Video Solution
Exercise #3

What is the area of the triangle in the drawing?

5557778.68.68.6

Step-by-Step Solution

First, we will identify the data points we need to be able to find the area of the triangle.

the formula for the area of the triangle: height*opposite side / 2

Since it is a right triangle, we know that the straight sides are actually also the heights between each other, that is, the side that measures 5 and the side that measures 7.

We multiply the legs and divide by 2

5×72=352=17.5 \frac{5\times7}{2}=\frac{35}{2}=17.5

Answer:

17.5

Video Solution
Exercise #4

Calculate the area of the following triangle:

444555AAABBBCCCEEE

Step-by-Step Solution

The formula for calculating the area of a triangle is:

(the side * the height from the side down to the base) /2

That is:

BC×AE2 \frac{BC\times AE}{2}

We insert the existing data as shown below:

4×52=202=10 \frac{4\times5}{2}=\frac{20}{2}=10

Answer:

10

Video Solution
Exercise #5

Calculate the area of the following triangle:

666777AAABBBCCCEEE

Step-by-Step Solution

The formula for the area of a triangle is

A=hbase2 A = \frac{h\cdot base}{2}

Let's insert the available data into the formula:

(7*6)/2 =

42/2 =

21

Answer:

21

Video Solution

Frequently Asked Questions

What is the trigonometric formula for triangle area?

+
The trigonometric formula for triangle area is Area = (1/2)ab sin(C), where 'a' and 'b' are two sides of the triangle and 'C' is the included angle between them. This formula works for all types of triangles.

How do you calculate triangle area when given two sides and an angle?

+
To calculate triangle area with two sides and an angle: 1) Identify the two given sides (a and b), 2) Find the included angle (C) between these sides, 3) Apply the formula Area = (1/2)ab sin(C), 4) Calculate sin(C) using your calculator, 5) Multiply and divide by 2 for the final answer.

Why use trigonometry instead of base times height for triangle area?

+
Trigonometry is used when you don't know the height of the triangle directly. The formula Area = (1/2)ab sin(C) allows you to find area using only two sides and the included angle, which is often more practical in real-world problems.

What angle should I use in the trigonometric area formula?

+
Always use the included angle - the angle that lies between the two given sides. If you have sides AB and AC, use angle A (the angle at vertex A). Using the wrong angle will give an incorrect result.

Does the trigonometric area formula work for all triangle types?

+
Yes, the formula Area = (1/2)ab sin(C) works for all triangles: right triangles, isosceles triangles, scalene triangles, acute triangles, and obtuse triangles. It's a universal formula for triangle area calculation.

How do I convert degrees to use in trigonometric calculations?

+
Most calculators handle degrees directly - just ensure your calculator is in degree mode. If working with radians, multiply degrees by π/180. For example, 60° = 60 × π/180 = π/3 radians.

What if I get a negative result using the trigonometric area formula?

+
Area cannot be negative. If you get a negative result, check that: 1) You're using the correct included angle, 2) Your calculator is in the right mode (degrees/radians), 3) You've identified the correct sides. The sine of any angle in a triangle is always positive.

Can I use this formula if I only know one side of the triangle?

+
No, you need at least two sides and the included angle to use Area = (1/2)ab sin(C). If you only have one side, you'll need additional information like another side, another angle, or the triangle's height to calculate the area.

More Area of a Triangle Questions

Continue Your Math Journey

Practice by Question Type