Question

show that sin^4theta - cos^4 theta = 1-2 cos^2 theta

Answer 1

this might be ur answer

Answer 2

${sin}^{2} \alpha - cos {}^{2} \alpha \times \sin^{2} \alpha + \cos {}^{2} \alpha \\ = 1 - cos {}^{2} \alpha \ - \cos^{2} \alpha \times 1 \\ = 1 - 2cos {}^{2} \alpha$