(cos A + cos B)² +(sin a - sin B )² in cosine
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Formula used = (a±b)² = a²+b²±2ab
→ cos²A + cos²B + 2cosAcosB + sin²A + sin²B - 2sinAsinB
→ Since cos²x + sin²x = 1
Therefore
→ 1+1+ 2(cosAcosB - sinAsinB)
→ 2 + 2cos(A+B)
→ cos²A + cos²B + 2cosAcosB + sin²A + sin²B - 2sinAsinB
→ Since cos²x + sin²x = 1
Therefore
→ 1+1+ 2(cosAcosB - sinAsinB)
→ 2 + 2cos(A+B)
alok148:
but in term of cosine
since '2' ks constant therefore whole term is in cosine form
i can't understand
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