evaluate without using trigonometric tables
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write sin^2 56= cos^2 34
tan72 = cot18
sin^2 34 + cos^2 34 + 2tan18 cot18 - cot^2 30
1+2tan18(1/tan18) -cot^2 30
1+2 -cot^2 30
3-cot^2 30
3-(root3)^2
3-(3)
=0 is answer
tan72 = cot18
sin^2 34 + cos^2 34 + 2tan18 cot18 - cot^2 30
1+2tan18(1/tan18) -cot^2 30
1+2 -cot^2 30
3-cot^2 30
3-(root3)^2
3-(3)
=0 is answer
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