If-the-angle-between-the-vectors-c-ai-2j-and-d-3i-j-is-45-find-the-two-possible-values-of-a-

Question Number 190811 by otchereabdullai last updated on 12/Apr/23

I f t h e a n g l e b e t w e e n t h e v e c t o r s

c = a i + 2 j a n d d = 3 i + j i s 45 °, f i n d

t h e t w o p o s s i b l e v a l u e s o f a

Answered by safojontoshtemirov last updated on 12/Apr/23

c = (a; 2) d = (3; 1)

c d =∣ c ∣∣ d ∣ c o s a

3 a + 2 = \sqrt{a^{2} + 4} \cdot \sqrt{5}

9 a^{2} + 12 a + 4 = 5 a^{2} + 20

4 a^{2} + 12 a - 16 = 0

a^{2} + 3 a - 4 = 0

a = - 4 a = 1

Commented by otchereabdullai last updated on 12/Apr/23

G o d b l e s s y o u s i r!