The x is going to be a negative number to get the 3. so start off minus 5 from plus 5 and minus five from the other side too. the positive 5 and the negative cancel out and then take it fromt here with three and the negative 5.
Simply you can substitute theta=45 degrees (or any angle,not zero) in left hand side and right hand side.
or
using a^2 - b^2 =(a+b)(a-b)
= sin(2x+x)sin(2x-x)
= sin 3x sin x
If you would like to know what is y when x = 42, you can calculate this using the following steps:
x = 8 ... y = 20
x = 42 ... y = ?
8 * y = 20 * 42 /8
y = 20 * 42 / 8
y = 105
The correct result would be: y = 105 when x = 42.
Your answer is A !! go for it !!
70/2=35 (this is the quotient)
60-35=25
