To find the angle formed at the base of the triangle after cutting the cardstock paper diagonally, we can use trigonometric relationships, specifically the tangent function.
Given:
- Height (opposite side) = 5 inches
- Base (adjacent side) = 3.5 inches
We can use the tangent function:
\[ \tan(\theta) = \frac{\text{opposite}}{\text{adjacent}} = \frac{5}{3.5} \]
Now, calculate the tangent value:
\[ \tan(\theta) = \frac{5}{3.5} \approx 1.4286 \]
Next, we need to find the angle \(\theta\) that corresponds to this tangent value by using the arctangent function:
\[ \theta = \tan^{-1}(1.4286) \]
Using a calculator to find this:
\[ \theta \approx 55° \]
Thus, the angle formed at the base of the triangle is approximately 55°.