Question

cos70°×cos20°-sin70°×sin20°​

Answer 1

Answer:

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Answer 2

Answer:

cos90=0 so your ans is 0

Step-by-step explanation:

let a=70 and b=20

we know that cos(a+b)=cos(a)×cos(b) - sin(a)×sin(b)

(this is an trigonometry identity)

so if u see carefully cos70×cos20-sin70×sin20 is same as cos(a)×cos(b) - sin(a)×sin(b) with a=70 and b=20

so cos(a+b)=cos(70+20)=cos90=0

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