Question

If the co-ordinates of the vertices of a triangle ABC are
(0,0), (cosa , sin a),(- sin a , cosa), then find <BAC.​

Answer 1

Answer:

90°

Step-by-step explanation:

in trangle ABC

let A: (0,0)

B : ( cosA, sinA)

C :( -sinA. ,cosA)

AB = √ (0- cosA)²+ (0- sinx)²= 1

BC= √( cosA+sinA)²+(cosA-sinA)²

√ 2(sin²A+cos²A)

= √2

CA= √ (0+sinA)²+(0-cosA)²

√( sin²A+ cos²A)

= 1

thus. ,. AB = 1, BC=√2, CA= 1

these are triplets , represent a rectangle

with base=1, perpendicular= 1, hypotenus= √2

therefore angle A= 90°