三角比,教下我(2)

a. sinθ = cos40°

sinθ = cos(90° - 50°)

sinθ = sin50°

θ = 50°


b. tanθ = cos0°

tanθ = 1

θ = 45°



a. sin60°

= √3/2

b. cos30°cos60°

= (√3/2)(1/2)

= √3/4

c. sin90°/cos²60°

= 1/(1/2)²

= 1/(1/4)

= 4

d. sin(90° - 30°)cos(90° - 30°)

= sin60°cos60°

= (√3/2)(1/2)

= √3/4

2007-07-10 20:30:21 補充：
求下列各題的值:呢啲係要記一記特別的度數，0度，30度，45度，60度，90度，配啲sin cos tan，會係咩數。記咗就會方便好多。或者可以用計算機~~~

你冇講到θ的範圍......我只能給你一個通解.....你代所有的n也會得到正確的ans
a. sinθ = cos40°
sinθ = sin50°
θ = 180°n+50°[(-1)^n] n是整數
b. tanθ = cos0°
tanθ = 1
θ = 180°n+45° n是整數
a. sin60°
= √3/2
b. cos30°cos60°
= (√3/2)(1/2)
= √3/4
c. sin90°/cos²60°
= 1/(1/2)²
= 4
d. sin(90°-30°)cos(90°-30°)
= sin60°cos60°
= (√3/2)(1/2)
= √3/4