In triangle XYZ Z = 90[sup]o[/sup], z = 140 mm, y = 70 mm. What is X?
[color=#ff0000][b]60[sup]o[/sup][/b][/color][br][br]Remember, Capital letters are for angles, lowercase letters are for sides, and a side has the same letter as the angle which is opposite it.[br]Drawing a sketch can be helpful.[br][br][img]https://image.ibb.co/e7Ng4v/Q10.jpg[/img][br]From the diagram it is clear to see 140 mm is the [b][color=#0000ff]H[/color][/b]ypotenuse. 70 mm is [b][color=#0000ff]A[/color][/b]djacent to angle [math]\theta[/math].[br][br]We know SOH C[b][color=#0000ff]AH[/color][/b] TOA. So we must use Cos as this uses the A and the H.[br][br][math]cos\theta=\frac{adj}{hyp}[/math][br][br]So, [math]cos\theta=\frac{70}{140}[/math][br][br]So, [math]\theta=cos^{-1}\frac{70}{140}=60^o[/math][br]