Final answer:
To calculate the size of angle feta in the isosceles triangle, use the fact that the sum of the angles in a triangle is 180 degrees. By using the given information and trigonometric functions, we can find the value of feta. The size of angle feta is approximately 178.646 degrees.
Step-by-step explanation:
To calculate the size of angle feta in the isosceles triangle, we can use the fact that the sum of the angles in a triangle is 180 degrees. Since the triangle is isosceles, the two base angles are equal. Let's call each base angle x. So, we have x + x + feta = 180.
Using the given information, we know that d0 = 7.50 cm and 1/d¡ = -0.2333 cm. Since do is the opposite side of angle feta, we can use the tangent function to solve for feta. tan(feta) = do/f, so tan(feta) = -0.2333/(-10.0). Taking the inverse tangent, we find that feta ≈ -1.354 degrees.
However, angles are usually measured in positive degrees, so we can convert the negative angle to positive by adding 180 degrees. Therefore, the size of angle feta is approximately 178.646 degrees.