prove that cos theta cos theta/ 2 - cos 3 theta cos 9 theta/2 = sin 4 theta sin 7 - Maths - Trigonometric Functions

Question

prove that cos theta cos theta/ 2 - cos 3 theta cos 9 theta/2 = sin
4 theta sin 7 theta/2 plzzzz

Neha Sethi · Accepted Answer

Dear student
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Note:sin-x=-sinxcosA-cosB=-2sinA+B2sinA-B22cosAcosB=cosA+B+cosA-B
Regards

prove that cos theta cos theta/ 2 - cos 3 theta cos 9 theta/2 = sin 4 theta sin 7 theta/2 plzzzz