devarshi-dt-logo

Question:

Choose the correct option and justify your choice: sin2A = 2sinA is true when A = 0, 30, 45, 60

30∘

0∘

45∘

60∘

Solution:

The correct option is A = 0

sin2A = 2sinA given
2sinAcosA = 2sinA (∵sin2A = 2sinAcosA)
2sinAcosA - 2sinA = 0
2sinA(cosA - 1) = 0
Either sinA = 0 or cosA - 1 = 0
A = 0 or cosA = 1 ⇒ A = 0
Hence, option A is correct.