It is known that in RT △ ABC, ∠ C = 90 ° CoSb = 23, then the value of SINB is () A. 253B. 53C. 255D. 55

∵ in △ ABC, ∠ C = 90 °, CoSb = 23, ∵ SINB = 1 − (23) 2 = 53

In the RT triangle ABC, the angle c = 90 ° (1) sin B = 3 / 5, a = 6, then Tan a (2) if a = 6, B = 8, then Sina= (3) if cosa = 1 / 3, B = 4, then a= (4) a = 12, C = 13, then tanb= (5) Sina = 3 / 5, then cosa= (6) Tana = 3 / 4, then Sina= (7) if angle A: angle B: angle c = 1:2:3, then a: B: C=__ .

(1)tanA=4/3
(2)sinA=3/5
(3) A = root 2
(4)tanB=5/12
(5)cosA=4/5
(6)sinA=3/5
(7)a:b:c=sin 30:sin60:sin90

As shown in the figure, in the triangle ABC, AB equals AC, ad is the height of BC, ad equals 18, be equals 15, find the length of BC

Let BD = x, ab = AC = y
Because AB2 = ad2 + BD2
So y * y = x * x + 18 * 18
1/2*2x*18=1/2*15y
BC=2*x

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