-98×191
compute using (a + b) (c+d)
=ac-ad-bc-bd(step by step explanation plz)
Answers
Answer:
Answer:
\text{The length of diagonals 40 cm and length of BC is }20\sqrt3=34.6 cmThe length of diagonals 40 cm and length of BC is 20
3
=34.6cm
Step-by-step explanation:
Given a rectangle ABCD in which AB=20 cm and ∠BAC=60°
we have to find the length of side BC and diagonals AC and BD.
In ΔABC, by trigonometric ratios
\cos\angle A=\frac{base}{hypotenuse}=\frac{AB}{AC}cos∠A=
hypotenuse
base
=
AC
AB
\cos 60=\frac{20}{AC}cos60=
AC
20
\frac{1}{2}=\frac{20}{AC}
2
1
=
AC
20
AC=20\times 2=40 cmAC=20×2=40cm
As diagonals of rectangles are equal
⇒ AC=BD=40 cm
\tan\angle A=\frac{Perpendicular}{Base}=\frac{BC}{AB}tan∠A=
Base
Perpendicular
=
AB
BC
\tan60^{\circ}=\frac{BC}{20}tan60
∘
=
20
BC
\sqrt3=\frac{BC}{20}
3
=
20
BC
BC=20\sqrt3=34.6 cmBC=20
3
=34.6cm