Referring to the is a way to estimate the wind speed.

Beaufort Scale

Explanation:

Sir Francis Beaufort, an Irish hydrographer, devised a scale to measure the wind speed in 1805. He devised this scale when he was serving on HMS Woolwich. Known as Beaufort Wind Force Scale, it measures and relates the speed of wind to conditions observed at land or sea. It was first used and officially adopted in 1830 on HMS Beagle where Robert Fitzroy was the captain.

No standard scale was present before the Beaufort scale. Initially, it had 13 classes (0-12) which related the wind condition quality and its effects on sails of a frigate. It was further extended in 1946 with addition of 5 more classes (13 to 17). Although, nowadays this extended scale is used only in mainland China and Taiwan.

Wind speed (as per 1946 scale):

m/s

where,

v = equivalent speed of wind 10m above the surface of the sea

B = Beaufort Scale number

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.

a and b sometimes have a positive value