How do you find the exact value of #sin60cos20-cos60sin20# using the sum and difference, double angle or half angle formulas?

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Answer 1 · 2017-03-24T09:13:05

#sin60^@cos20^@-cos60^@sin20^@=0.6428#

We use here the difference formula #sinAcosB-cosAsinB=sin(A-B)#

let #A=60^@# and #B=20^@#

then using the formula

#sin60^@cos20^@-cos60^@sin20^@#

= #sin(60^@-20^@)#

= #sin40^@#

= #0.6428#