The value of sin 40 degrees is 0.64278760968 as seen on a calculator. The sine, cosine and tangent are all based on the right-angled triangle and are useful calculations in trigonometry.
These three functions have common abbreviations where sine is "sin", cosine is "cos" and tangent is "tan". The sine function can be found by using the following equation: sin (degree) = opposite / hypotenuse. The "opposite" and "hypotenuse" refer to the sides of the triangle that the angle is in. "Opposite" is opposite to the angle's degree and "hypotenuse" is the longest side of the triangle. "Adjacent" is adjacent or next to the angle's degrees and is used in the cos and tan calculations.