2020年6月15日 · cos 80 degrees = 0.17365. The cos of 80 degrees is 0.17365, the same as cos of 80 degrees in radians. To obtain 80 degrees in radian multiply 80° by / 180° = 4/9 . Cos 80degrees = cos (4/9 × . Our results of cos80° have been rounded to five decimal places. If you want cosine 80° with higher accuracy, then use the calculator below; our tool ...

2017年10月8日 · How to prove that cos (80°)+cos(40°)-cos(20°)=0 ? Trigonometry. 1 Answer Narad T. Oct 8, 2017 See the ...

2017年10月5日 · 1/8. cos20^@cos40^@cos80^@, =1/(2sin20^@)(2sin20^@cos20^@)cos40^@cos80^@, =1/(2sin20^@)sin(2xx20^@)cos40^@cos80^@, =1/(4sin20^@)(2sin40^@cos40^@)cos80^@, …

2017年10月8日 · We know, cos C - cos D = - 2 sin(C + D)/2. sin (C - D)/2. Hence, #[ cos 80 - cos 40]/sin 40# #rArr [ - 2 sin (80+40)/2. sin (80-40)/2]/sin 40#

2018年5月29日 · tan^2 40 Use trig identities: 1 - cos 2a = 2sin^2 a 1 + cos 2a = 2cos^2 a In this case: 1 - cos 80 = 2sin^2 40 1 + cos 80 = 2cos^2 40 Therefor, (1 - cos 80)/(1 + cos 80) = tan^2 40 Trigonometry Science

2018年6月1日 · How do you use an addition or subtraction formula to write the expression as a trigonometric function of one number and then find the exact value given #cos(80)cos(10)-sin(80)sin(10)#? Trigonometry Trigonometric Identities and …

2018年4月21日 · #cos80^@-cos40^@+sqrt3cos70^@=?# #cosA-cosB=-2sin((A+B)/2)sin((A-B)/2)# #cos80^@-cos40^@=-2sin((80^@+40^@)/2)sin((80^@-40^@)/2)=-2sin60^@sin20^@=-2(sqrt3)/2sin20 ...

2016年9月26日 · This formula can be simplified to -sin60=-sqrt(3)/2 sin20cos80-cos20sin80=sin(20-80)=sin(-60)=-sin60=-sqrt(3)/2

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2018年6月2日 · LHS=sin10sin30sin50sin70 =cos(90-10)sin30cos(90-50)cos(90-70) =cos(80)*1/2*cos(40)cos(20) =1/(4 sin20)cos(80)cos(40)*2sin20cos(20) =1/(8 sin20)cos(80)*2cos(40)sin(40 ...