Trigonometric radio.

22. sin θ = 3/5


圖片參考：http://imgcld.yimg.com/8/n/HA08074410/o/701208100043613873414090.jpg

By the Pyth. Theorem, √5² - 3² = 4

cos θ = 4/5, tan θ = 3/4

23. AB/AC = cos 60°
AB/6 = cos 60°
AB = 6 cos 60° = 3

By the Pyth. Theorem, BC = √AC² - AB²
= √6² - 3² = √27 = 3√3

24. cos θ = 0.1 = 1/10


圖片參考：http://imgcld.yimg.com/8/n/HA08074410/o/701208100043613873414091.jpg



By the Pyth. Theorem, √10² - 1² = √99 = 3√11

∴ sin θ = (3√11)/10, tan θ = (3√11)/1 = 3√11

25. sin 30° - (tan 30°/cos 45°) x sin 60°
= 1/2 - (1/√3 ÷ 1/√2) x √3/2
= 1/2 - (√2/√3) x √3/2
= 1/2 - √2/2
= 1/2 (1 - √2)

26. tan 22° = BC/AB
tan 22° = 15 cm /AB
AB = (15/tan 22°) cm = 37.1263028 cm

∴The area of the triangle = 1/2 x AB x BC
= (1/2 x 37.1263028 x 15) = 278.447271 cm² ≈ 278 cm², cor. to nearest integer.

22.
sinθ=3/5
cosθ=√(1-sin^2θ)=√[1-(3/5)^2]=4/5
tanθ=sinθ/cosθ=(3/5)/(4/5)=3/4
23.
cos60°=AB/6
AB=6cos60°=6x1/2=3.
tan60°=CB/3
CB=3tan60°=3√3
24.
cosθ=0.1=1/10
sinθ=√(1-cos^2θ)=√[1-(1/10)^2]=√99/10
tanθ=sinθ/cosθ=(√99/10)/(1/10)=√99
25.
sin30°-tan30°/cos45°xsin60°
=1/2-(√3/3)/(√2/2)x(√3/2)
=(1-√2)/2
26.
tan22°=15/BA
BA=15/tan22° cm
∴The area of the triangle=(1/2)(15)(15/tan22°)=278cm^2(corr.to nearest integer)