What is half the vertical distance from the crest to the trough of a transvers wave?

It is the amplitude.

Explanation:

The amplitude is the measure of the size of the disturbance from a wave, so half the distance from the trough and crest.

igneous rocks also form where plates converge. the subducting plate melts as it sinks into the crust of the earth, and the melt rises into the overriding plate forming volcanoes. metamorphic rocks are formed mainly in the lithosphere, wherever there is high pressure and high temperature. -woods

the answer to this is proletariats.

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