Practicing Success
If sinA + cos2A = \(\frac{1}{3}\) cosA + sin2A = \(\frac{1}{4}\), then find the value of (sin3A). |
\(\frac{-59}{72}\) \(\frac{-59}{36}\) \(\frac{-263}{288}\) 0 |
\(\frac{-263}{288}\) |
Square both the equation: ⇒ sin2A + cos22A + 2sinA cos2A =\(\frac{1}{9}\) ⇒ cos2A + sin22A + 2cosA sin2A =\(\frac{1}{16}\) Now, add the equations: ⇒ 1 + 1 + 2sin(2A + A) = \(\frac{1}{9}\)+\(\frac{1}{16}\) ⇒ 2 + 2sin3A =\(\frac{25}{144}\) ⇒ 2(sin3A) = \(\frac{25}{144}\)-2 ⇒ sin3A = \(\frac{-263}{288}\) |