Answer:
∠ ABC = 81° , ∠ FEC = 90°
Step-by-step explanation:
Since AB ≅ BC then Δ ABC is isosceles.
The median BE is therefore
The angle bisector of ∠ ABC and
BE bisects AC at right angles.
Thus
∠ ABE = ∠ CBE = 40° 30' , then
∠ ABC = 2 × 40° 30' = 81°
Since BE is perpendicular to AC then
∠ FEC = 90°
15×4=60 and 3 people will be left without a group of 4
A. Cos2x
f(x) = sin(x)cos(x) = (1/2) sin(2x) using double angle formula.
f'(x) = ( (1/2)sin(2x) )' = 2(1/2)cos(2x) = cos(2x)
