How much would need to be deposited into an account earning 4.7%, compounded semi-annually, so that the balance will be $1,000,000.00 in 20 years

When x = 0° :    sin x = 0, cos x = 1, therefore sin x * cos x = 0.
Also, when x = 90° :  sin x = 1, cos x = 0,  so sin x * cos x = 0.
For any value between 0° and 90° , the product of sin and cos is less than 1.
We can show it like this:
sin 2 x = 2 sin x cos x ( trigonometric formula )
sin x cos x = 1
sin 2 x / 2 = 1  / * 2 ( we will multiply both sides of an equation by 2 )
sin 2 x = 2 This is impossible because the maximum value for sin of any angle is 1.
sin x cos x is never equal to 1.