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【急】想問兩題幾何(10分)
發問:
想問兩題幾何..f.2程度=] (1)已知△ABC的周長是12cm, c+a=2b, c-a=2cm, a, b, c各等于多少?(三元一次) (2)根據下列條件, 求△ABC∠C的大小 a. ∠A=65°40' , ∠B=36°25' b. ∠B=∠C=2∠A c. ∠A=105°, ∠B–∠C=15° d. ∠A=∠B=∠C 各位幫幫我啦，我想要整個過程 > 更新: 各位幫幫我啦，我想要整個過程=]
最佳解答:
1) 首先要知道的是角A對面的邊是a,角B對面的邊是b,如此類推。 c + a = 2b --------------1) c - a = 2 cm -----------2) a + b + c = 12 cm ---3) From 2), c = 2 + a ---4) Put 4) into 3), a + b + 2 + a = 12 2a + b = 10---------------5) Put 4) into 1), 2 + a + a = 2b b = a + 1 -----------------6) Put 6) into 5), 2a + a + 1 = 10 3a = 9 a = 3 Put a = 3 into 6), b = 3 + 1 b = 4 Put a = 3 and b = 4 into 3), 3 + 4 + c = 12 c = 5 2) a. ∠A + ∠B + ∠C = 180.....(∠ sum of triangle) 65 + 36 + ∠C = 180 ∠C = 79 b. ∠A + ∠B + ∠C = 180.....(∠ sum of triangle) ∠A + 2∠A + 2∠A = 180 5∠A = 180 ∠A = 36 Therefore, ∠C = 36 x 2 ∠c = 72 c. ∠A + ∠B + ∠C = 180.....(∠ sum of triangle) ∠A + ∠C + 15 + ∠C = 180 120 + 2∠C = 180 ∠C = 30 d. ∠A + ∠B + ∠C = 180.....(∠ sum of triangle) 3∠C = 180 ∠C = 60
其他解答:
【急】想問兩題幾何(10分)
發問:
想問兩題幾何..f.2程度=] (1)已知△ABC的周長是12cm, c+a=2b, c-a=2cm, a, b, c各等于多少?(三元一次) (2)根據下列條件, 求△ABC∠C的大小 a. ∠A=65°40' , ∠B=36°25' b. ∠B=∠C=2∠A c. ∠A=105°, ∠B–∠C=15° d. ∠A=∠B=∠C 各位幫幫我啦，我想要整個過程 > 更新: 各位幫幫我啦，我想要整個過程=]
最佳解答:
1) 首先要知道的是角A對面的邊是a,角B對面的邊是b,如此類推。 c + a = 2b --------------1) c - a = 2 cm -----------2) a + b + c = 12 cm ---3) From 2), c = 2 + a ---4) Put 4) into 3), a + b + 2 + a = 12 2a + b = 10---------------5) Put 4) into 1), 2 + a + a = 2b b = a + 1 -----------------6) Put 6) into 5), 2a + a + 1 = 10 3a = 9 a = 3 Put a = 3 into 6), b = 3 + 1 b = 4 Put a = 3 and b = 4 into 3), 3 + 4 + c = 12 c = 5 2) a. ∠A + ∠B + ∠C = 180.....(∠ sum of triangle) 65 + 36 + ∠C = 180 ∠C = 79 b. ∠A + ∠B + ∠C = 180.....(∠ sum of triangle) ∠A + 2∠A + 2∠A = 180 5∠A = 180 ∠A = 36 Therefore, ∠C = 36 x 2 ∠c = 72 c. ∠A + ∠B + ∠C = 180.....(∠ sum of triangle) ∠A + ∠C + 15 + ∠C = 180 120 + 2∠C = 180 ∠C = 30 d. ∠A + ∠B + ∠C = 180.....(∠ sum of triangle) 3∠C = 180 ∠C = 60
其他解答:
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