In 1844, Charles Goodyear obtained the first patent for a rubber condom.
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The shortest mature adult human of whom there is independent evidence was Gul Mohammed in India. In 1990, he was measured in New Delhi and stood 22.5 inches tall.
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Sperm cells are so tiny that 400 to 500 million (400,000,000–500,000,000) of them fit onto 1 tsp.
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Approximately one in three babies in the United States is now delivered by cesarean section. The number of cesarean sections in the United States has risen 46% since 1996.
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Each year in the United States, there are approximately six million pregnancies. This means that at any one time, about 4% of women in the United States are pregnant.
One page of color vision chart.
How to plot a sine function containing an amplitude and phase shift (Question 1 of 3)
How to solve a trigonometric problem involving two right triangles (Question 1)