Question

let us show that cos 55° cos 45°— sin 55° sin 35° = 0 .​

Answer 1

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ANSWER✍

Cos55° cos35° —Sin55° sin35°

=> Cos (90° – 35°) cos35° – sin (90° –35° ) sin35°

=> Sin35° cos35° – Cos35° sin 35° = 0 (proved)

hope it's help you✌

Answer 2

SOLUTION

We know that

=) cosA cosB -sinA sinB= cos(A+B)

Now,

=) sin35 sin55 -cos35 cos55

=) -(cos35 cos55 - sin35 sin55)

=) -[cos (35+55)]

=) -cos90

=) 0 PROVED

HOPE IT HELPS