Prove that - cos 65 - - cos 115 - - 0

LHS=cos 65^∘+cos 115^∘=2cos(115^∘+65^∘2)cos(115^∘ 65^∘2)=2cos 90^∘cos 25^∘=0=RHS ...

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Trigonometric Ratios of Allied Angles

Prove that : ...

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Prove that : $cos 65^{\circ} + cos 115^{\circ} = 0$

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\sin 65 ° + \cos 65 ° = \sqrt{2} \cos 20 °

Show that :
(i) $\sin 50 ° \cos 85 ° = \frac{1 - \sqrt{2} \sin 35 °}{2 \sqrt{2}}$

(ii) $\sin 25 ° \cos 115 ° = \frac{1}{2} (\sin 140 ° - 1)$

The distance between the points $(a c o s 25^{\circ}, 0)$ and $(0, a c o s 65^{\circ})$ is ___.

(a c o s 25^{\circ}, 0)

(0, a c o s 65^{\circ})

sin 25^{\circ} cos 115^{\circ} = (sin 40^{\circ} - 1)

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