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प्रश्न
Without using trigonometric tables, prove that:
cos257° − sin233° = 0
उत्तर
LHS = cos257° − sin233°
= cos2 (`90^circ - 33^circ`) - sin2 `33^circ`
= sin2 `33^circ` - sin2 `33^circ`
= 0
= RHS
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