10) En un triángulo rectángulo ABC, B es un ángulo
1 answer:
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Let
point A----------------- > Bob
point B----------------- > lamppost that is to Bob left
point C----------------- > lamppost that is to Bob right
we know that
dAB=25 ft
dAC=30 ft
dBC=20 ft
see the attached figure
we use the law of cosines------------- > dBC²=dAB² +dAC² -2(dAB)(dAC)cos(alfa)
we have that
20²=25² +30² -2(25)(30)cos(alfa)-------- > cos (alfa)=(20²-(25² +30²))/(-2*25*30)
cos (alfa)=(400-(625 +900))/(-1500)= (400-(625 +900))/(-1500)=1125/1500=0.75
<span>alfa=arccos (0.75)= 41.4096 -------- > 41 °-------- > </span>∡ BAC
the answer is 41 °