What marked the starting point of world war i?

The assassination of Archduke Franz Ferdinand.

Explanation:

Franz Ferdinand, the Archduke of Austria, was assassinated by Gavrilo Princip, a Bosnian Serb nationalist. This provoked Austria-Hungary to declare war on Serbia, which brought about World War I.

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°