2/5×1/4=2/20find the mistake and correct it

Which sum or difference identity would you use to verify that cos (180° - ∅) = -cos ∅? a. sin (α -β) = sin α cos β – cos α sin β b. cos (α -β) = cos α cos β – sin α sin β c. cos (α -β) = cos α cos β + sin α sin β d. sin (α + β) = sin α cos β + cos α sin β

For the inequality |c| < |d| to be true, which of the following must be true?

What is the value of x in the equation 1.5x+4-3=4.5(x-2)?