Decimal places are the spaces present after a decimal, denoted by the . in a number. This means, if I had 1.2 the 2 is in the first decimal place. In 3.1415 , the 5 is in the 4th decimal place. It is also commonly called, in respective order, the tenths place, the hundreds place, the thousandths place, and so on. For example, in 1.432 the 4 is in the tenths place, the 3 is in the hundredths place, and the 2 is in the thousandths place.
We have the formula (sin x)^2 + (cos x)^2 = 1; Then, sin α = cos β = We apply the formula sin ( α + β ) = sin α x cos β + sin β x cos α = (3/5)x(4/5) + (4/5)x(3/5) = 12/25 + 12/25 = 24/25;