For how many positive three-digit integers is the product of their three digits 90?
1 answer:
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Answer:
x=πn, n∈Z
Step-by-step explanation:
if sin²2x=1-cos²2x, then
1-cos²2x-2cos2x+2=0; ⇒ cos²2x+2cos2x-3=0; ⇔ (cos2x+3)(cos2x-1)=0;