(a) Prove geometrically that cos (A + B) cos A cos B-sin Asin BHence f – InterviewSolution

1.	(a) Prove geometrically that cos (A + B) cos A cos B-sin Asin BHence find cos 75°
Answer» cos75°=cos(45°+30°)=cos45°cos30°-sin30°sin45° = (1/√2)(√3/2)-(1/2)(1/√2)=(√3-1)/2√2

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