Q16 of 113 Page 560

Prove that

(cos x – cos y)2 + (sin x – sin y)2 = 4 sin2


= (cos x – cos y)2 + (sin x – sin y)2


=(-2sinsin) 2 +(2cossin) 2


=4 sin2(sin2+cos2)


=4 sin2


Using the formula,


cosA - cosB = -2sinsin


sinA - sinB = 2cos sin


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