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Question
Express each one of the following in terms of trigonometric ratios of angles lying between 0° and 45°
sin 67° + cos 75°
Solution
We know that `sin(90^@ - theta) = cos theta` and `cos(90^@ - theta) = sin theta` So
`sin 67^@ + cos 75^@ = sin(90^@ - 23^@) + cos(90^@ - 15^@)`
`= cos 23^@ + sin 15^@`
Thus the desired expression is `cos 23^@ + sin 15^@`
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