Suppose eratosthenes had found that, in alexandria, at noon on the first day of summer, the line to the sun makes an angle 30° with the vertical. what, then, would he have found for earth’s circumference?

6000 miles

Explanation:

The angle of the sun shone at an angle of 30° to the zenith

This means that the angle of the sector of the circle is 30° (θ)

S = Length of the sector of the circle = 500 miles (Distance between Alexandria and Syene)

r = radius of earth

Converting 30° to radians

Circumference

∴ Earth’s circumference would have been 6000 miles

explanation: magnetic pole, region at each end of a magnet where the external magnetic field is strongest. the south-seeking pole, or any pole similar to it, is called a south magnetic pole. unlike poles of different magnets attract each other; like poles repel each other.

i think it because equal matrices have equal dimensions, only square matrices can be symmetric. for all indices and . every square diagonal matrix is symmetric, since all off-diagonal elements are zero. in linear algebra, a real symmetric matrix represents a self-adjoint operator over a real inner product space.