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Why don't we have eclipses every month?

Answer 1

Eclipses happen when Earth, Moon and Sun comes in a straight line.

The lunar orbit around Earth is tilted 5.8 degrees to ecliptic apparent path of Sun. Moon goes round the Earth once in 27 days 8 hours. But full moon to full moon is 29.5 days.

Eclipses happen only at the point of intersection of both these orbits called nodes.

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Answer 2

Harper Clark

Eclipses only happen when the alignment of the Earth, Moon, and Sun is such that the Earth passes through the shadow cast by the Moon (lunar eclipse) or when the Moon passes between the Earth and the Sun, casting its shadow on Earth (solar eclipse). Because the Moon's orbit around the Earth is inclined relative to the Earth's orbit around the Sun, this means that most of the time, the Moon's shadow misses the Earth or falls above or below the Earth, resulting in no eclipse.

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Answer from HIX Tutor

When evaluating a one-sided limit, you need to be careful when a quantity is approaching zero since its sign is different depending on which way it is approaching zero from. Let us look at some examples.