Answer:
Step-by-step explanation:

we take the LHS so here goes,

since ,
the identity becomes,

now, we know,
and 
the identity becomes,


sin A and cos A cancel out it becomes zero

Splitting the denominator the identity becomes

Hence,

Dot product is
a*b = |a|*|b|*cosα.
In our case
u*u =|u|*|u|*cos 0
u*u =|u|*|u|
12=|u|²
|u|=√12=√(4*3)=2√3
Answer: <span>D. 2√3</span>
Could I see the shape? I don’t think you uploaded the image to see the shape above.
Length:12 cm
Width: 7 cm
My work is shown in the picture. I hope this helps!