Yes, a chenille sweater should be hand washed to ensure that it retains its softness and shape. Chenille fabric is delicate and can be easily damaged in a washing machine, so hand washing is the best way to care for it. Use a gentle detergent and lukewarm water, and avoid wringing or twisting the sweater to prevent stretching or distortion. After washing, gently squeeze out excess water and lay the sweater flat to dry. **

A polar day is a period of 24 hours of continuous daylight that occurs in the polar regions during the summer months. This phenomenon happens because the Earth's axial tilt causes the sun to never fully set below the horizon at these latitudes during this time of year. On the other hand, a polar night is a period of 24 hours of continuous darkness that occurs in the polar regions during the winter months. This happens because the Earth's axial tilt causes the sun to never rise above the horizon at these latitudes during this time of year. **

The polar day and polar night occur in the polar regions near the North and South Poles. During the polar day, the sun does not set and remains visible for 24 hours a day, while during the polar night, the sun does not rise and the region experiences 24 hours of darkness. These phenomena are a result of the tilt of the Earth's axis and its orbit around the sun, causing extreme variations in daylight hours in these regions. **

Polar days and polar nights occur in the polar regions near the North and South Poles. During polar days, the sun does not set and remains visible for 24 hours a day, while during polar nights, the sun does not rise and the region remains in darkness for 24 hours a day. These phenomena are a result of the tilt of the Earth's axis and its orbit around the sun, causing extreme variations in daylight hours in the polar regions. **

Polar substances dissolve in polar substances because they have similar intermolecular forces. Polar substances, such as water, have a partial positive and partial negative charge, which allows them to form hydrogen bonds with other polar molecules. When a polar substance is added to a polar solvent, the partial charges on the solvent molecules attract and surround the solute molecules, causing them to separate and disperse evenly throughout the solvent. This allows the polar solute to dissolve in the polar solvent, forming a homogeneous mixture. **

Polar day and polar night occur in the polar regions, specifically within the Arctic and Antarctic Circles. During polar day, the sun remains above the horizon for a continuous 24 hours, resulting in 24 hours of daylight. Conversely, during polar night, the sun remains below the horizon for a continuous 24 hours, resulting in 24 hours of darkness. These phenomena are caused by the tilt of the Earth's axis and its orbit around the sun. **

The task is to prove the trigonometric identity that tan(x1+x2) = (tan(x1) + tan(x2)) / (1 - tan(x1)tan(x2)). This involves using the sum of angles formula for tangent and manipulating the expression to show that the left-hand side is equal to the right-hand side. By simplifying both sides of the equation and showing that they are equal, we can confirm that the identity is correct. **

The polar day occurs during the summer solstice in the polar regions, which is around June 21st in the Northern Hemisphere and December 21st in the Southern Hemisphere. During this time, the sun does not set for 24 hours, resulting in continuous daylight. Conversely, the polar night occurs during the winter solstice in the polar regions, which is around December 21st in the Northern Hemisphere and June 21st in the Southern Hemisphere. During this time, the sun does not rise for 24 hours, resulting in continuous darkness. **