Question

If vectors P, Q and R have magnitudes 5, 12 and 13 units and P+ Q =R, the angle between Q and R is
in terms of cos

Answer 1

Answer:

The answer is 21.25 ° .

Explanation:

Solution:

P = 5

Q = 12

R = 13

To find angle between Q & R

P + Q = R

P = R - Q ( Talking square on both sides)

P2 = R2 + Q 2 - 2QRCosΘ

(5)2 = (13)2 + (12)2 -2(12)(13) CosΘ

25 = 169 + 144 - 312 CosΘ

25 - 313 = -312CosΘ

  - 288 = - 312CosΘ

Minus sign cancels out on both sides.

CosΘ = 288/312

Reducing the number to the lowest.

CosΘ = 12/13

  Θ   = Cos-1 (12/13)

  Θ   = Cos-1 (0.932)

  Θ   = 21.25 °

Answer 2

Answer:

|vector p |=5

|vector q |=12

|vector R|=13

cos theta = q/R =12/13

theta =cos^-1(12/13)

this is the answer

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