tan 9°-tan 27°-tan 63°+tan 81 ° is equal to

We have,tan⁡9∘−tan⁡27∘−tan⁡63∘+tan⁡81∘=tan⁡9∘+tan⁡81∘−tan⁡27∘+tan⁡63∘=tan⁡9∘+cot⁡9∘−tan⁡27∘+cot⁡27∘=1sin⁡9∘cos⁡9∘−1sin⁡27∘cos⁡27∘=2sin⁡18∘−2sin⁡54∘=2sin⁡54∘−sin⁡18∘sin⁡54∘sin⁡18∘=2cos⁡36∘−sin⁡18∘sin⁡18∘cos⁡36∘=4