Select the statement that is true: 1) history is best explained by eras, or time periods. 2) history need not include themes such as conflict, cooperation, industrialization - this is another social science. 3) all history is interrelated and inseparable. 4)history should only be studied as regions such as european, american, greek, etc.

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°

a countries leader should be motivated by the common good of the country.