C-09-Q176mediumsingle_mcqcos230∘+cos260∘=?\cos^2 30^\circ + \cos^2 60^\circ = ?cos230∘+cos260∘=?a000b12\dfrac{1}{2}21c111d32\dfrac{\sqrt{3}}{2}23ব্যাখ্যাUsing cos230∘=34\cos^2 30^\circ=\tfrac34cos230∘=43 and cos260∘=14\cos^2 60^\circ=\tfrac14cos260∘=41, the sum is 34+14=1\tfrac34+\tfrac14=143+41=1. (Note 30∘30^\circ30∘ and 60∘60^\circ60∘ are complementary, so this is also cos2θ+sin2θ=1\cos^2\theta+\sin^2\theta=1cos2θ+sin2θ=1.)