Answer:
Step-by-step explanation:
We are to show that 
<u>Proof:</u>
From trigonometry identity;


From trigonometry, 2sinAcosA = Sin2A

Also note that sin(B-C) = sinBcosC - cosBsinC
sin420cos140 - cos420sin140 = sin(420-140)
The resulting equation becomes;

= 
If you add all the numbers on the right together you get -35 then you divide by 5 which gives you the average of -7*F
Answer:
f(4) = 6
Step-by-step explanation:
f(x) = 3x - 6
f(4) = 3(4) - 6
f(4) = 12 - 6
f(4) = 6
Answer:
7j+7
Step-by-step explanation:
2j+4j+j+7
combine like terms
7j+7
Sorry I don't really know how to explain it, but you just have to combine terms with the same unit