OA and BO are two vectors of magnitudes 5 and 6 respectively. If angle B O A=60°, then 0 A ⋅ O B is equal to

Question

OA and BO are two vectors of magnitudes 5 and 6 respectively. If angle B O A=60°, then 0 A ⋅ O B is equal to (A) 15 (B) 0 (C) 15 √ 3 (D) -15

Tardigrade Admin · Accepted Answer

We have magnitudes of OA and OB are 5 and 6 respectively And angle BOA=60° Now, O A ⋅ O B =| O A | ⋅ O B mid cos θ ⇒ 0 A ⋅ O B =5 ⋅ 6 ⋅ cos 60° ⇒ O A ⋅ O B =30 × (1/2) ⇒ OA ⋅ O B =15

Q. OA and BO are two vectors of magnitudes 5 and 6 respectively. If $∠ BO A = 6 0^{\circ}$ , then $0 A \cdot OB$ is equal to

$15$

$0$

$153$

$- 15$

We have magnitudes of $O A$ and $OB$ are 5 and 6 respectively
And $∠ BO A = 6 0^{\circ}$
Now, $O A \cdot OB = ∣ O A ∣ \cdot OB ∣ cos θ$
$\Rightarrow 0 A \cdot OB = 5 \cdot 6 \cdot cos 6 0^{\circ}$
$\Rightarrow O A \cdot OB = 30 \times \frac{1}{2}$
$\Rightarrow O A \cdot OB = 15$

Q. OA and BO are two vectors of magnitudes 5 and 6 respectively. If ∠BOA=60∘, then 0A⋅OB is equal to

15

0

153​

−15

We have magnitudes of OA and OB are 5 and 6 respectively And ∠BOA=60∘ Now, OA⋅OB=∣OA∣⋅OB∣cosθ ⇒0A⋅OB=5⋅6⋅cos60∘ ⇒OA⋅OB=30×21​ ⇒OA⋅OB=15

Q. OA and BO are two vectors of magnitudes 5 and 6 respectively. If $∠ BO A = 6 0^{\circ}$ , then $0 A \cdot OB$ is equal to

$15$

$0$

$153$

$- 15$

We have magnitudes of $O A$ and $OB$ are 5 and 6 respectively
And $∠ BO A = 6 0^{\circ}$
Now, $O A \cdot OB = ∣ O A ∣ \cdot OB ∣ cos θ$
$\Rightarrow 0 A \cdot OB = 5 \cdot 6 \cdot cos 6 0^{\circ}$
$\Rightarrow O A \cdot OB = 30 \times \frac{1}{2}$
$\Rightarrow O A \cdot OB = 15$