Between 1870 and 1890 which area had the greatest amount of railroad expansion

 The correct answer is :  the Western states

Explanation:  The expansion of the railroad affected the environment at the end of the 19th century because many western forests were cut down to build railroads and bridges. The expansion of the railroad helped the prices of goods in the golden age to decrease as the shipment of products by rail was much cheaper.

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°