cos x . cos 2x

is gelijk aan
A.    cos 3x
B.      sin 2x
  ———  
      2. sin x
C.     sin 3x
  ———
     3. sin x
D.     sin 4x
   ———    
    4. sin x
E.  2 (cos x + cos 3x)
A    B    C    D    E 

[ 5-2191 - op net sinds 23.7.2020-(E)-4.11.2023 ]

Translation in   E N G L I S H

IN CONSTRUCTION

Oplossing - Solution

Het antwoord is D want

gricha