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If cos4α - sin4α = $$\frac{5}{6}$$ then the value of 2cos2α - 1 = . . . . . . . .
Answer & Solution
Correct Answer:
Option
B
cos4α - sin4α = $$\frac{5}{6}$$
(cos2α + sin2α)(cos2α - sin2α) = $$\frac{5}{6}$$
1 × (cos2α - 1 + cos2α) = $$\frac{5}{6}$$
2cos2α - 1 = $$\frac{5}{6}$$
(cos2α + sin2α)(cos2α - sin2α) = $$\frac{5}{6}$$
1 × (cos2α - 1 + cos2α) = $$\frac{5}{6}$$
2cos2α - 1 = $$\frac{5}{6}$$
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