Right side of the equation:
cos ( A - B ) - cos ( A + B ) =
= cos A cos B + sin A sin B - ( cos A cos B - sin A sin B ) =
= cos A cos B + sin A sin B - cos A cos B + sin A sin B =
= 2 sin A sin B - left side of the equation ( correct )
Multiply both sides of the equation by 20. 2z-3-5(z-6)=60. 2z-3-5z+30=60. -3z-3+30=60. -3z+27=60. -3z=60-27. -3z=33. Divide both sides by 3. Answer is: Z= -11
X^2+8x=10
X^2+8x-10=0
(X^2+8x+16-16)-10=0
(X^2+8x+16)-16-10
(X+4)^2-26
Hope this helps!
Set up an equation when x is the cost of a book. If we know that 45 + 5 = 50:
45x = 50(x - .1)
Now, multiply across the parentheses:
45x = 50x - 5 (Now, combine terms over the equal sign)
-50x -50x
-5x = -5 (Now, divide off the -5 from both sides)
/-5 /-5
x = 1
This means that the current cost of a book is <em><u>$1.</u></em> This works out if you test it.
Hope this helps!
~<em>ArchimedesEleven</em>
