What was so significant about windmills during the 1st industrial revolution?

It became the first reliable inanimate source of energy. It also helped to undermine the traditional classical view that all energy had to come from animals or humans. The first windmills were used for irrigation and grinding grain. Eventually they would power the medieval textile industry.

angle a = 40.6°

step-by-step explanation:

for any right angle triangle we know the pythagoras theorem reveals

hypotenuse² = height²+base²

by this formula we will calculate the length of hypotenuse

h² = 6²+7²

⇒ h =√36+49 = √85 = 9.22

now from the given triangle sin a = height/ hypotenuse

                                                sin a = 6/9.22 = 0.651

therefore

so angle a = 40.6°

bismarck believed in using force

is the correct answer!