Iam an odd 4-digit number between 5,000 and 5,999. the digit in the thousands place is half of the smallest 2-digit number and the digit in the tens place is a multiple of 4, greater than 4. the digit in the hundreds place is the greatest 1-digit number and the digit in the ones place is 2 less than the hundreds digit. what number am i?

You are 5,987. 5 in the thousands place because you are a number in the 5,000s, and also the smallest 2 digit number divided 2 makes 5. 9 in the hundreds place because the biggest 1 digit number is 9. 8 in the tens place because the only single digit number that is a multiple of 4, but not 4, is 8. 7 in the ones place because 9 is the hundreds place, minus 2 is 7.

see explanation

Step-by-step explanation:

Using the double angle identity for sine

sin2x = 2sinxcosx

Consider left side

cos20°cos40°cos80°

= (2sin20°cos20°)cos40°cos80°

= (2sin40°cos40°)cos80°

= (sin80°cos80° )

= (2sin80°cos80° )

= . sin160°

= . sin(180 - 20)°

= . sin20°

= = right side , thus proven