Question

it's urgent

cos^2 15- sin^2 45
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Answer 1

Step-by-step explanation:

To find cos245o−sin215o

We know that, cos2θ=2cos2θ−1⟹cos2θ=21+cos2θ

And cos2θ=1−2sin2θ⟹sin2θ=21−cos2θ

∴cos245o=21+cos(2×45)=21+cos90o=21+0=21

Also, ∴sin215o=21−cos(2×15)=21−cos30o=21−23=