CUET PG 2023 — Mathematics PYQ
CUET PG | Mathematics | 2023Each of the angle between vectors a,b and c is equal to 60∘ if ∣a∣=4,∣b∣=2 and ∣c∣=6 then the modulus of a+b+c is
Choose the correct answer:
- A.
10
(Correct Answer) - B.
15
- C.
12
- D.
20
10
Explanation
Step 1: Modulus ka Square nikalna
Sabse pehle hum ∣a+b+c∣2 ka formula likhte hain:
∣a+b+c∣2=∣a∣2+∣b∣2+∣c∣2+2(a⋅b+b⋅c+c⋅a)
Step 2: Dot Products calculate karna
Humein pata hai ki cos(60∘)=21, toh individually dot products honge:
-
a⋅b=4×2×21=4
-
b⋅c=2×6×21=6
-
c⋅a=6×4×21=12
Step 3: Values ko formula mein rakhna
Ab saari values ko equation mein substitute karte hain:
∣a+b+c∣2=42+22+62+2(4+6+12)
∣a+b+c∣2=16+4+36+2(22)
∣a+b+c∣2=56+44
∣a+b+c∣2=100
Step 4: Final Result
Square root lene par:
∣a+b+c∣=100=10
Explanation
Step 1: Modulus ka Square nikalna
Sabse pehle hum ∣a+b+c∣2 ka formula likhte hain:
∣a+b+c∣2=∣a∣2+∣b∣2+∣c∣2+2(a⋅b+b⋅c+c⋅a)
Step 2: Dot Products calculate karna
Humein pata hai ki cos(60∘)=21, toh individually dot products honge:
-
a⋅b=4×2×21=4
-
b⋅c=2×6×21=6
-
c⋅a=6×4×21=12
Step 3: Values ko formula mein rakhna
Ab saari values ko equation mein substitute karte hain:
∣a+b+c∣2=42+22+62+2(4+6+12)
∣a+b+c∣2=16+4+36+2(22)
∣a+b+c∣2=56+44
∣a+b+c∣2=100
Step 4: Final Result
Square root lene par:
∣a+b+c∣=100=10

