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chapter4.2r
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à 4.2ïSimplifying Trigonometric Expressions
äïPlease simplify the following trigonometric expressions.
#âêêêë 1 - cosìΘ
#êêêèSimplifyï─────────
êêêêê sin Θ
#êêë1 - cosìΘêsinìΘ
#êêë─────────è=è─────è=èsin Θ
êêêsin Θêïsin Θ
éSïIn the last section we saw the eight fundamental trigonometric
identities.ïThese identities can be used to algebraically simplify
other expressions involving trigonometric functions.
è In the example, you are asked to simplify the expression
#(1 - cosìΘ)/sin Θ.ïSince the Pythagorean identity, sinìΘ + cosìΘ = 1,
#can be changed to, sinìΘ = 1 - cosìΘ, it is permissible to replace
#1 - cosìΘ with sinìΘ.
#êêë1 - cosìΘêsinìΘ
#êêë─────────è=è─────è=èsin Θ
êêêsin Θêïsin Θ
#Thus, (1 - cosìΘ)/sin Θ simplifies to sin Θ.
1êêêë sin Θ
#êêêëSimplifyï─────
êêêêê tan Θ
ê A)ïcos ΘêëB)ïsec ΘêïC)ïå of ç
ü
êêêêsin Θ/tan Θ
êêêè=èsin Θ/(sin Θ/cos Θ)
êêêè=èsin Θ ∙ (cos Θ/sin Θ)
êêêè=ècos Θ
Ç A
# 2êêêë 1 - sinìΘ
#êêêëSimplifyï─────────
êêêêêècos Θ
ê A)ïtan ΘêëB)ïcos ΘêïC)ïå of ç
ü
#êêêê(1 - sinìΘ)/cos Θ
#êêêè=ècosìΘ/cos Θ
êêêè=ècos Θ
Ç B
3êêêë cos Θ
#êêêëSimplifyï─────
êêêêê tan Θ
êA)ïcsc Θ - sin ΘëB)ïsin Θ + cos Θè C)ïå of ç
ü
êêêêcos Θ/tan Θ
êêêè=ècos Θ/(sin Θ/cos Θ)
êêêè=ècos Θ ∙ (cos Θ/sin Θ)
#êêêè=ècosìΘ/sin Θ
#êêêè=è(1 - sinìΘ)/sin Θ
#êêêè=è1/sin Θ - sinìΘ/sin Θ
êêêè=ècsc Θ - sin Θ
Ç A
4êêêë cot Θ
#êêêëSimplifyï─────
êêêêê csc Θ
êA)ïcos Θêë B)ïsec Θêè C)ïå of ç
ü
êêêêcot Θ/csc Θ
êêêè=è(cos Θ/sin Θ)/(1/sin Θ)
êêêè=è(cos Θ/sin Θ) ∙ sin Θ
êêêè=ècos Θ
Ç A
5
êêêëSimplifyïtan Θ ∙ csc Θ
êA)ïcot Θêë B)ïsec Θêè C)ïå of ç
ü
êêêêtan Θ ∙ csc Θ
êêêè=è(sin Θ/cos Θ)∙(1/sin Θ)
êêêè=è1/cos Θ
êêêè=èsec Θ
Ç B
6êêêêèsin Θ
#êêêëSimplifyï1 - ─────
êêêêêëcsc Θ
#êA)ïsec Θêë B)ïcosìΘêè C)ïå of ç
ü
êêêê1 - sin Θ/csc Θ
êêêè=è1 - sin Θ ∙ sin Θ
#êêêè=è1 - sinìΘ
#êêêè=ècosìΘ
Ç B
7êêêê 1ê1
#êêêëSimplifyï───── + ─────
#êêêêê secìΘècscìΘ
êA)ï1êè B)ïcot Θ ∙ tam ΘêïC)ïå of ç
ü
#êêêê1/secìΘ + 1/cscìΘ
#êêêè=ècosìΘ + sinìΘ
êêêè=è1
Ç A
8
#êêêSimplifyïsecìΘ - sinìΘ ∙ secìΘ
#êïA)ïsecìΘ ∙ tan ΘêB)ï1êè C)ïå of ç
ü
#êêêêsecìΘ - sinìΘ ∙ secìΘ
#êêêè=è1/cosìΘ - sinìΘ ∙ 1/cosìΘ
#êêêè=è(1 - sinìΘ)/cosìΘ
#êêêè=ècosìΘ/cosìΘ
êêêè=è1
Ç B