Maths problem, thanks?

Question

☂雨後晴空☀ · Accepted Answer

△ABC : △ADE = AC : AE 
△ABC :  1  = (AC/AD) : (AE/AD)
△ABC = (1/cos60°) :  cos60°
△ABC = 2 : 1/2
△ABC = 4 cm²
The answer is B.

SC147 · Answer

∠B=∠E=90⁰
∠BAC=30⁰=∠EDA
∠BCA=60⁰=∠EAD
∴ △ABC ～ △DEA  (AAA)
=> area of △ABC ：area of △DEA =AC² ：DA² 
=> area of △ABC ：1 = AC² ：DA² 
=> area of △ABC = (AC/DA)² . . . . . . . . . . . . . . . ① 
　　　　　　　　　　　　　　　DA
From rt-angled △ADC, cos 60⁰ = ------
　　　　　　　　　　　　　　　AC
　　　　　　　　　　 　　½  = DA/AC 
　　　　　　　　　
From ①： area of △ABC = (2/1)² = 4　　(ans : B )

一對眼看著你 · Answer

△ABC : △ADE = AC : AE 
△ABC : 1 = (AC/AD) : (AE/AD) 
△ABC = (1/cos60°) : cos60° 
△ABC = 2 : 1/2 
△ABC = 4 cm² 
The answer is B

WONG · Answer

△ABC : △ADE = AC : AE 
△ABC : 1 = (AC/AD) : (AE/AD) 
△ABC = (1/cos60°) : cos60° 
△ABC = 2 : 1/2 
△ABC = 4 cm² 
The answer is B.

家駒 · Answer

△ADE ～ △CAB

area△ADE : area△ABC = AD ² : AC ² = 1² : 2² = 1 : 4

4cm²

B. #

匿名 · Answer

The answer is B

Maths problem, thanks?

6 個解答