1971-11-30 — Page 26

報日橘茶

#BSTAT#SEL WAH KIU YAT PO

二期星日十三月一十年一七九一层公年十六國 民承中實教備華

育敎僑華

Let us look at the following

or (308).

1972英文中學會考試題預習專欄。

堅道英文書院主編

Solution

[(1)(a)

(0)

數學科

Mathemation

(0) 323

(2) sin(p

Cos(

(五)

sin(180 - 2) Cos(180

sind

2012

ᎭᎾ

General angle

The general angle angle of any sze

(including negative

angles

It should be noticed that the position OP can

be arrived at by

turning through

any number of

complete turns.

plus the angle

A

19 our convention

that all p091-1]UG.

angles are obtained:

by turning in an

anti-clockivise direction. from OX and negative angl direction from OX

turning in a clockivise,

"We are going to investigate the sine, Cosine and

tangent of the angles (1) - 9 (11) 90-0 (111) 90 +6 and the others may be referred to some standard text

the subjec".

Q(xy)

[Q (x, y)

constructed in

ko une figurus ♬ ind 90·0: standard pos1 Tign and 0Q OQ In each of the figures

the two triangles ine congruent and

sin(90

Cos U

3(x y z

| Cos(90

tan(90

Summarizing all these resulta,

we have

(xy)

Cosa 360 tan (360

sing Сов

where n

re OT

ад

tan

OF KOJO,j

In O

the diagrama, 8 and 90 -♬ are constructed: efandard position and 00 -

In each of the

tan

Coa O

-tan.

diagrama the two triangles are congruent and

sin (90

Cos (90

can (90)

Cos

sin (90

Coa

Opa (90)

tan (90)

Cos (90

a(xy)

In the above figures, and are constructed to @tandard position and they are equal aumerically 4100 00 - 0Q - In each of the figures, the two triangles are congruent and

Thenj

Etan (90

For the investigation of the functions of 90 we refer to the following figures,

The formulas for the functions of 270- and 270 can be derived from the above results

sin(270 –► ) - sia (180 + (90 - 0)] = -sin(90 -A) - Cos(270-6) Cos (180) ► ·-0)]= -30s(30 -0) = -sing tan(270 - 0) tan 80 ) (90 - 0)1 tan(90 -0

Cote

914(270 + 8) = sin (180 (90 + d)]- -vin(90 +0) -Cos◊

Cos(2700) , còn 180 (90 + Đ], _Cos(90 + D) sao

Can(270

tan iso

190

©)jo tan(90 + 0) = -Cot

COB (

Coa

Can

9000

Sxercise

(1) Express each of the following in terms of

trigonometrical functions of a positive acute, ▼ Lane! in, two ways

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