(1)sin765(2)cos(-1020)(3)tan(97π/6)(4)cot(-39π/6)(5)sin(-120
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(1)sin765
(2)cos(-1020)
(3)tan(97π/6)
(4)cot(-39π/6)
(5)sin(-120)tan(-120)+cos(-135)cot(420)+sin(3π/2)
要用诱导公式!
(2)cos(-1020)
(3)tan(97π/6)
(4)cot(-39π/6)
(5)sin(-120)tan(-120)+cos(-135)cot(420)+sin(3π/2)
要用诱导公式!
sin764=sin(360*2+45)=sin45=√2/2
cos(-1020)=cos(360*3-1020)=cos60=1/2
tan(97π/6=tan(96π/6+π/6)=tan(π/6)=√3/3
cot(-39π/6)=cot(42π/6-39π/6)=cot(2/π)=0
sin(-120)tan(-120)+cos(-135)cot(420)+sin(3π/2)=
-sin(-120+180)tan(180-120)-cos(180-135)cot(420-360)-1
=-sin60tan60-cos45tan60-1
=-3/2-√6/2
cos(-1020)=cos(360*3-1020)=cos60=1/2
tan(97π/6=tan(96π/6+π/6)=tan(π/6)=√3/3
cot(-39π/6)=cot(42π/6-39π/6)=cot(2/π)=0
sin(-120)tan(-120)+cos(-135)cot(420)+sin(3π/2)=
-sin(-120+180)tan(180-120)-cos(180-135)cot(420-360)-1
=-sin60tan60-cos45tan60-1
=-3/2-√6/2
(1)sin765(2)cos(-1020)(3)tan(97π/6)(4)cot(-39π/6)(5)sin(-120
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