Question
Find the value of the following:sin(36° + A) ×
cos(54° – A) + cos(36° + A) × sin(54°–A)Solution
sin(36° + A) × cos(54° – A) + cos(36° + A) × sin(54°–A)
We know that, sin(X + Y) = sinX × cos Y + cosX × sinY
Similarly, sin(36° + A) × cos(54° – A) + cos(36° + A) × sin(54°–A) = sin{(36 o  + A) + (54 o  – A)}
= sin(36 o  + A + 54 o  – A) = sin90 o  = 1
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