The bisector of angle B of parallelogram ABCD intersects side AD at point K so that AK = 6, AD = 8.
March 29, 2021 | education
| The bisector of angle B of parallelogram ABCD intersects side AD at point K so that AK = 6, AD = 8. Find the area of the parallelogram if the angle B is 150 degrees
Corners B and C – one-sided inner:
<B + <C = 180 °;
<C = 180 ° – <B = 180 ° – 150 ° = 30 °.
The opposite angles of the parallelogram are:
<A = <B = 30 °.
The bisector BG divides <B in half:
<ABG = <CBG = <B / 2 = 150 ° / 2 = 75 °;
<AGB = 180 ° – <A – <ABG = 180 ° – 30 ° – 75 ° = 75 °;
<ABG = <AGB.
It follows from the equality of the angles that ΔABG is isosceles:
AG = AB = 6 cm.
The height BH of the parallelogram is omitted from point B. ΔABH is rectangular. The BH leg is opposite the angle A = 30 °:
BH = AB / 2 = 6/2 = 3 cm.
SABCD = AD * BH = 8cm * 3cm = 24cm ^ 2.
Answer: 24 cm ^ 2.
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