Calculate the diagonals and an angle of a parallelogram given two sides and an angle.
|Mathematics
Calculate the diagonals and an angle of a parallelogram given two sides and an angle.
ScanSolve AI Answer
Answer
7.82 cm
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Question 8:
Given a parallelogram with sides 8 cm and 10 cm, and the angle between them is 130∘. Let the parallelogram be ABCD, with AB = 8 cm, AD = 10 cm, and ∠DAB=130∘.
In a parallelogram, consecutive angles are supplementary, so ∠ABC=180∘−130∘=50∘.
a) Calculate the diagonals of the parallelogram.
Step 1: Calculate the length of diagonal AC using the cosine rule in △ABC.
Sides are AB = 8 cm, BC = AD = 10 cm, and ∠ABC=50∘.
AC2=AB2+BC2−2(AB)(BC)cos(∠ABC)AC2=82+102−2(8)(10)cos(50∘)AC2=64+100−160(0.6428)AC2=164−102.848AC2=61.152AC=61.152≈7.82 cm
Step 2: Calculate the length of diagonal BD using the cosine rule in △ABD.
Sides are AB = 8 cm, AD = 10 cm, and ∠DAB=130∘.
BD2=AB2+AD2−2(AB)(AD)cos(∠DAB)BD2=82+102−2(8)(10)cos(130∘)BD2=64+100−160(−0.6428)BD2=164+102.848BD2=266.848BD=266.848≈16.34 cm
The diagonals are approximately 7.82cm and 16.34cm.
b) Calculate angle DBC.
Step 3: Calculate ∠DBC using the cosine rule in △BCD.
In △BCD, BC = 10 cm, CD = AB = 8 cm, and BD = 16.34 cm.
Let ∠DBC=θ.
CD2=BC2+BD2−2(BC)(BD)cos(θ)82=102+(16.34)2−2(10)(16.34)cos(θ)64=100+266.9956−326.8cos(θ)64=366.9956−326.8cos(θ)326.8cos(θ)=366.9956−64326.8cos(θ)=302.9956cos(θ)=326.8302.9956≈0.9271θ=arccos(0.9271)≈21.95∘
The angle ∠DBC is approximately 21.95∘.
Question 9:
One side of rhombus ABCD is 8 cm in length. If ∠DAB=64∘, find BD and AC.
In a rhombus, all sides are equal, so AB = BC = CD = DA = 8 cm.
Step 1: Find diagonal BD using the cosine rule in △ABD.
Sides are AB = 8 cm, AD = 8 cm, and ∠DAB=64∘.
BD2=AB2+AD2−2(AB)(AD)cos(∠DAB)BD2=82+82−2(8)(8)cos(64∘)BD2=64+64−128(0.4384)BD2=128−56.0992BD2=71.9008BD=71.9008≈8.48 cm
Step 2: Find diagonal AC.
In a rhombus, consecutive angles are supplementary, so ∠ABC=180∘−64∘=116∘.
Use the cosine rule in △ABC.
Sides are AB = 8 cm, BC = 8 cm, and ∠ABC=116∘.
AC2=AB2+BC2−2(AB)(BC)cos(∠ABC)AC2=82+82−2(8)(8)cos(116∘)AC2=64+64−128(−0.4384)AC2=128+56.0992AC2=184.0992AC=184.0992≈13.57 cm
The diagonals are BD ≈8.48 cm and AC ≈13.57 cm.
Question 10:
ABCD is a rhombus. ∠ABC=140∘, and AB = 20 cm. Calculate (a) AC and (b) ∠ACB.
In a rhombus, all sides are equal, so AB = BC = CD = DA = 20 cm.
a) Calculate AC.
Step 1: Find diagonal AC using the cosine rule in △ABC.
Sides are AB = 20 cm, BC = 20 cm, and ∠ABC=140∘.
AC2=AB2+BC2−2(AB)(BC)cos(∠ABC)AC2=202+202−2(20)(20)cos(140∘)AC2=400+400−800(−0.7660)AC2=800+612.8AC2=1412.8AC=1412.8≈37.59 cm
The length of AC is approximately 37.59cm.
b) Calculate ∠ACB.
Step 2: Calculate ∠ACB.
In △ABC, AB = BC = 20 cm, so it is an isosceles triangle.
The base angles are equal: ∠BAC=∠BCA.
The sum of angles in a triangle is 180∘.
∠BAC+∠BCA+∠ABC=180∘2×∠ACB+140∘=180∘2×∠ACB=180∘−140∘2×∠ACB=40∘∠ACB=240∘=20∘
The angle ∠ACB is 20∘.
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ScanSolve AI Answer
Morning ♡tasha♡....🧸 — let's get this done. Question 8: Given a parallelogram with sides 8 cm and 10 cm, and the angle between them is 130^. Let the parallelogram be ABCD, with AB = 8 cm, AD = 10 cm, and DAB = 130^. In a parallelogram, consecutive angles are supplementary, so ABC = 180^ - 130^ = 50^. a) Calculate the diagonals of the parallelogram. Step 1: Calculate the length of diagonal AC using the cosine rule in ABC. Sides are AB = 8 cm, BC = AD = 10 cm, and ABC = 50^. AC^2 = AB^2 + BC^2 - 2(AB)(BC)( ABC) AC^2 = 8^2 + 10^2 - 2(8)(10)(50^) AC^2 = 64 + 100 - 160(0.6428) AC^2 = 164 - 102.848 AC^2 = 61.152 AC = sqrt(61.152) ≈ 7.82 cm Step 2: Calculate the length of diagonal BD using the cosine rule in ABD. Sides are AB = 8 cm, AD = 10 cm, and DAB = 130^. BD^2 = AB^2 + AD^2 - 2(AB)(AD)( DAB) BD^2 = 8^2 + 10^2 - 2(8)(10)(130^) BD^2 = 64 + 100 - 160(-0.6428) BD^2 = 164 + 102.848 BD^2 = 266.848 BD = sqrt(266.848) ≈ 16.34 cm The diagonals are approximately 7.82 cm and 16.34 cm. b) Calculate angle DBC. Step 3: Calculate DBC using the cosine rule in BCD. In BCD, BC = 10 cm, CD = AB = 8 cm, and BD = 16.34 cm. Let DBC = . CD^2 = BC^2 + BD^2 - 2(BC)(BD)() 8^2 = 10^2 + (16.34)^2 - 2(10)(16.34)() 64 = 100 + 266.9956 - 326.8() 64 = 366.9956 - 326.8() 326.8() = 366.9956 - 64 326.8() = 302.9956 () = (302.9956)/(326.8) ≈ 0.9271 = (0.9271) ≈ 21.95^ The angle DBC is approximately 21.95^. Question 9: One side of rhombus ABCD is 8 cm in length. If DAB = 64^, find BD and AC. In a rhombus, all sides are equal, so AB = BC = CD = DA = 8 cm. Step 1: Find diagonal BD using the cosine rule in ABD. Sides are AB = 8 cm, AD = 8 cm, and DAB = 64^. BD^2 = AB^2 + AD^2 - 2(AB)(AD)( DAB) BD^2 = 8^2 + 8^2 - 2(8)(8)(64^) BD^2 = 64 + 64 - 128(0.4384) BD^2 = 128 - 56.0992 BD^2 = 71.9008 BD = sqrt(71.9008) ≈ 8.48 cm Step 2: Find diagonal AC. In a rhombus, consecutive angles are supplementary, so ABC = 180^ - 64^ = 116^. Use the cosine rule in ABC. Sides are AB = 8 cm, BC = 8 cm, and ABC = 116^. AC^2 = AB^2 + BC^2 - 2(AB)(BC)( ABC) AC^2 = 8^2 + 8^2 - 2(8)(8)(116^) AC^2 = 64 + 64 - 128(-0.4384) AC^2 = 128 + 56.0992 AC^2 = 184.0992 AC = sqrt(184.0992) ≈ 13.57 cm The diagonals are BD ≈ 8.48 cm and AC ≈ 13.57 cm. Question 10: ABCD is a rhombus. ABC = 140^, and AB = 20 cm. Calculate (a) AC and (b) ACB. In a rhombus, all sides are equal, so AB = BC = CD = DA = 20 cm. a) Calculate AC. Step 1: Find diagonal AC using the cosine rule in ABC. Sides are AB = 20 cm, BC = 20 cm, and ABC = 140^. AC^2 = AB^2 + BC^2 - 2(AB)(BC)( ABC) AC^2 = 20^2 + 20^2 - 2(20)(20)(140^) AC^2 = 400 + 400 - 800(-0.7660) AC^2 = 800 + 612.8 AC^2 = 1412.8 AC = sqrt(1412.8) ≈ 37.59 cm The length of AC is approximately 37.59 cm. b) Calculate ACB. Step 2: Calculate ACB. In ABC, AB = BC = 20 cm, so it is an isosceles triangle. The base angles are equal: BAC = BCA. The sum of angles in a triangle is 180^. BAC + BCA + ABC = 180^ 2 × ACB + 140^ = 180^ 2 × ACB = 180^ - 140^ 2 × ACB = 40^ ACB = (40^)/(2) = 20^ The angle ACB is 20^. Send me the next one 📸