Question

If a, b, g be the angles which a line makes with the positive direction of co-ordinate axes, then sin²a + sin²b + sin²g =

• A. 2
• B. 1
• C. 3
• D. 0

Answer 1

Answer: (A)

2

Answer 2

cos2a + cos2b + cos2g

= 2cos²a – 1 + 2cos²b – 1 + 2cos²g – 1

= 2(cos²a + cos²b + cos²g) – 3 = – 1