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The cosine of an acute angle is equal to the sine of its complement.
sin 48^(∘)
Keep in mind that complementary angles add up to 90^(∘). To find the complement of 42, we subtract our given angle from 90. Now, we can rewrite cos 42^(∘) in terms of sine. cos 42^(∘) = sin(90^(∘)-42^(∘)) = sin 48^(∘)
