To calculate the surface area of a triangular pyramid (tetrahedron), we need to find both the area of the triangular base and the area of the three triangular faces.
- Area of the Base Triangle:
The base is a triangle with a base (b) of 4.5 units and an assumed height (h) we have to derive. Given the last angle of 3.9 degrees, we don’t have enough information about the shape of the triangle. Generally, the formula for the area of a triangle is given by:
\[ \text{Area} = \frac{1}{2} \times b \times h \]
Since we do not have the height, we will proceed with the pyramid’s lateral faces and then use the slant height to calculate the area of each of the lateral triangular faces.
- Area of the Lateral Faces:
Each triangular face has a base of 4.5 (the same as the base of the pyramid, assuming it is a right triangular pyramid) and a slant height of 3.5. The area of one triangular face is calculated as:
\[ \text{Area of one face} = \frac{1}{2} \times \text{base} \times \text{slant height} \] Substituting the values:
\[ \text{Area of one face} = \frac{1}{2} \times 4.5 \times 3.5 = \frac{15.75}{2} = 7.875 \]
Since there are three identical triangular lateral faces, the total lateral area is:
\[ \text{Lateral Surface Area} = 3 \times 7.875 = 23.625 \]
- Total Surface Area:
Now, we need to calculate the area of the base triangle. To do this, let's assume the triangle's area can be found using the height of the base (which we can derive from properties of triangles). However, to simplify the calculation, we will complete it in terms of an assumed height \( h_b \) until that information is made available.
For geometrical correctness, we will express the total surface area as:
\[ \text{Total Surface Area} = \text{Area of Base} + \text{Lateral Surface Area} \] If we assume the area of the base triangle as needing \( h_b \) for completion \( = \frac{1}{2} \times 4.5 \times h_b \), we can substitute:
\[ \text{Total Surface Area} = \frac{1}{2} \times 4.5 \times h_b + 23.625 \]
To get an exact number for total surface area without the concrete height measurement, we need the height of the triangular base or any additional angles.
Summary of Result:
Thus, the total surface area formula can be represented as:
\[ \text{Surface Area} = \frac{1}{2} \times 4.5 \times h_b + 23.625 \]
Where \( h_b \) is the height of the base triangle. If you can provide that information, we can calculate the exact surface area of the triangular pyramid.