Question

Prove
(Sin 80degrees) - (cos 70degrees) = cos 50 degrees

Answer 1

Step-by-step explanation:

sin 80° - cos 70°= cos 50°

=> sin 80° = cos 50° + cos 70°

now, RHS= cos 50°+cos70°

= 2cos{(50°+70°)/2}×cos{(70°-50°)/2}

=2cos60°×cos10°

=2×1/2×cos10°

=cos10°

=cos(90-80)°

=sin80°

=LHS

hence the proof is complete.

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