Thread: Stumped by this one

A hockey net is 1.83 m wide. A player shoots from a point where the puck is 13m from one goal post and 11.5m from the other. Within what angle must she make her shot to score?

Originally Posted by cinbad

A hockey net is 1.83 m wide. A player shoots from a point where the puck is 13m from one goal post and 11.5m from the other. Within what angle must she make her shot to score?

Use the cosine rule for this. You have the three sides of the triangle and
you need to find the angle between two of the sides.

RonL

Originally Posted by cinbad

A hockey net is 1.83 m wide. A player shoots from a point where the puck is 13m from one goal post and 11.5m from the other. Within what angle must she make her shot to score?

Here is one way.

Imagine, or draw the figure on paper.
It is a triangle whose 3 sides are 1.83, 13, and 11.5----all in meters.

You are asked to find the angle included by the 13m and 11.5m sides. Call that angle A.

Use the Law of Cosines.
a^2 = b^2 +c^2 -2bc*cosA
(1.83)^2 = (13)^2 +(11.5)^2 -2(13)(11.5)cosA
2(13)(11.5)cosA = (13)^2 +(11.5)^2 -(1.83)^2
cosA = [(13)^2 +(11.5)^2 -(1.83)^2] / [2(13)(11.5)]
cosA = 297.9011 /299
cosA = 0.996324749
A = arccos(0.996324749)
A = 4.914 degrees ----------------answer.