Question

Prove that cos square 15 degree minus cos square 30 degree + cos square 45 degree minus cos square 60 degree + cos square 75 degree is equal to 1 upon 2

Answer 1

Step-by-step explanation:

cos^2 15°-cos^2 30°+cos^2 45°-cos^2 60°+cos^2 75°=1/2

cos^2 15°=sin^2 75°(complementary angles)

sin^2 75°+cos^75°-cos^2 30°+cos^2 45°-cos^2 60°=1/2

1-1/4+1/2-3/4=1/2

4/4-1/4+2/4-3/4=1/2

(4-1+2-3)/4=1/2

2/4=1/2

1/2=1/2

Hence Proved

Answer 2

Step-by-step explanation:

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