(sinA)^2=sinB(sinB+sinC) A与B的关系是什么那个……第4步好像有些问题阿

(sinA)^2=sinB(sinB+sinC) A与B的关系是什么那个……第4步好像有些问题阿
(sinA)^2=sinB(sinB+sinC) A与B的关系是什么
那个……第4步好像有些问题阿

(sinA)^2=sinB(sinB+sinC) A与B的关系是什么那个……第4步好像有些问题阿
ABC是三角形的三个顶点吗~以下我是按它们是三角形顶点算的~
(sinA)²=sinB(sinB + sinC)
sin²A = sin²B + sinBsin(派-A-B)
sin²A - sin²B = sinBsin(A+B)
【呃~我错了~不好意思的说~中间加几步~】
(sinA + sinB)(sinA - sinB) = sinBsin(A+B)
2sin[(A+B)/2]cos[(A-B)/2] · 2cos[(A+B)/2]sin[(A-B)/2] = sinBsin(A+B) （和差化积）
sin(A+B)sin(A-B) = sinBsin(A+B) (倍角公式)
因为 sin(A+B)不为0,故 sin(A-B) = sinB
故 A-B = B 或 (A-B) + B = 派（舍）
所以,A=2B

Did You Know?
Behavior
Fast Facts

Population
Did You Know?
Reproduction
Mating season: Varies depending on the species.
Gestation: 9-15 months, depending o...

全部展开

Did You Know?
Behavior
Fast Facts

Population
Did You Know?
Reproduction
Mating season: Varies depending on the species.
Gestation: 9-15 months, depending on the species.
Number of offspring: 1 calf.
Nursing time is long (more than one year for many species), which is associated with a strong bond between mother and young. This strategy of reproduction spawns few offspring, but provides each with a high probability of survival in the wild.
Legal Status/Protection Various species of whales are listed under the Endangered Species Act (ESA) as either threatened or endangered. Many species of whales are included in either Appendices I or II of CITES, as well as listed on the IUCN Red List, depending on their current population. All whales are protected under the Marine Mammal Protection Act. Whales are protected under the International Convention for the Regulation of Whaling, Washington, December 2, 1946. Learn more about legal status and protection of whales >> How You Can Help Help whales and other wildlife by adopting a beluga whale at our Wildlife Adoption Center. Take Action for Wildlife at our Wildlife Action Center. For additional information Visit Defenders' Imperiled Species: Cook Inlet Beluga Whale and North Atlantic Right Whale pages for more information about what Defenders is doing to help these whales. North Atlantic Right Whale Fact Sheet Beluga Whale Fact Sheet World Conservation Union North Atlantic Marine Mammal Commission North Pacific Marine Science Organization Convention on International Trade in Endangered Species NOAA's National Marine Fisheries Service
Choose Next Fact Sheet -- Animals -- Alligator Arctic Fox Bald Eagle Bats Beluga Whale Bighorn Sheep Bison Black Bear Black-Footed Ferret Bobcat Burrowing Owl Butterflies Cactus Ferruginous Pygmy Owl California Condor Cerulean Warbler Channel Island Fox Cheetah Clouded Leopard Colorado River Basin Fish Crocodile Desert Tortoise Diamondback Terrapin Dolphin Elephant Fisher Frogs Fur Seal, Northern Gopher Tortoise Gorilla Grizzly Bear Hawaiian Monk Seal Hummingbirds Jaguar Lion Lobster, American Lynx Manatee Mexican Wolf Mohave Ground Squirrel Monarch Butterfly Mountain Goat Mountain Lion Narwhal Panda Panther Penguin Peregrine Falcon Polar Bear Prairie Dog, Black-Tailed Red Wolf Right Whale River Otter Salmon San Joaquin Kit Fox Sea Otter Sea Turtles Sharks Snow Leopard Snowy Owl Sonoran Pronghorn Spotted Owl, Mexican Spotted Owl, Northern Swift Fox Thick-Billed Parrot Tiger Vaquita Walrus Western Snowy Plover Whale Wolf, Gray Wolverine Woodland Caribou Woodpeckers Zebra -- Habitats -- Coral Reef Desert Forest Grasslands Marine Wetlands
Whaling is one of the biggest threats to whales. By the middle of the 20th century, whaling had left many populations severely depleted. The International Whaling Commission introduced a moratorium which continues to this day. However, there are still some exceptions to this moratorium. This allows countries like Norway, Iceland and Japan and the aboriginal communities of Siberia, Alaska and northern Canada to continue their annual whale hunts.
Defenders is currently hard a work on behalf of two highly endangered North American whale species. Learn more about our efforts to save the Cook Inlet beluga whale and the North Atlantic right whale.
Home > Wildlife and Habitat >
The Blue Whale is the largest known mammal that has ever lived, and the largest living animal, at up to 110 feet long and 150 tons.
Beneath the skin lies a layer of fat called blubber. It serves as an energy reservoir and also as insulation. Whales breathe through blowholes, located on the top of the head so the animal can remain submerged. Baleen whales have two blowholes,while toothed whales have one.
The diet of whales depends on their species; it can range from microscopic plankton to large marine mammals.

In addition, several species of small whales are caught as bycatch in fisheries for other species. Exposure to contaminants and pollution also threaten whales. Scientists also believe that underwater sonar testing by the navies of various countries leads to whale beachings. Mass whale beachings occur in many species, mostly beaked whales that use echolocation systems for deep diving. Whales are also threatened by climate change because higher water temperatures in the Antarctic Ocean are reducing populations of krill, a small-shrimp-like crustacean that is the main food source for some whale species.
Whale Facts and Sound - Cetacea - Defenders of Wildlife Sound Defenders At Work Take Action
Reasons For Hope
Global Warming and Other Threats

Whales are mammals, and as such, they have hair - though very little of it!

Length: Varies; up to 110 feet long.
Weight: Varies; up to 150 tons.
Lifespan: Generally 20-40 years, but can live up to 80 years; varies with each species.
Whales belong to the order cetacea, which includes whales, dolphins and porpoises. Whales are divided into two suborders: baleen and toothed whales. Baleen whales have a comb-like fringe, called a baleen, on the upper jaw, which is used to filter plankton, as well as small fish and crustaceans. They are the largest species of whale. Toothed whales have teeth and prey on fish, squid, other whales and marine mammals. They sense their surrounding environment through echolocation.
Oil Spills Kill
Sea Turtles Email Print Share
Range
Because of their environment (and unlike many animals) and because they need to breathe air by coming to the water's surface,chanel store, whales are conscious breathers, meaning they decide when to breathe. All mammals sleep,bvlgari shop, including whales, but they cannot afford to fall into an unconscious state for too long, since they need to be conscious to break the surface in order to breathe
Global warming's effects will be felt by most marine creatures, and whales are certainly not excluded. Sea level rise and changes in sea temperature will leave whales quite vulnerable, and they may not be able to adapt quickly enough to survive. Arctic and antarctic whale habitat faces a particular threat from climate change. Whale food sources will also face challenges, such as a decline in krill population,omega seamaster, which is the main food source for many large whale species.
Most whales are quite active in the water. They jump high,mbtshoes, or breach, out of the water and land back in the water. They also thrust their tails out of the water and slap the water's surface, which is believed to be a warning of danger nearby. Whales also communicate with each other using lyrical sounds. These sounds are extremely loud depending on the species and can be heard for many miles.
Diet
Defenders At Work

Varies with each species.
Many whales, especially baleen whales, tend to migrate long distances from their cold-water feeding grounds to warm-water breeding grounds each year. They travel alone or in groups, or pods, on their annual migrations. Toothed whales often hunt in groups, migrate together and share young-rearing duties.
In October 2008, Cook Inlet beluga whales, one of the most endangered species of whale, were thrown a life line by the National Marine Fisheries Service (NMFS), who announced that beluga whales will receive protection under the Endangered Species Act (ESA). The announcement followed a petition filed by a coalition of conservation groups back in March 1999 and massive public support, calling on the Bush administration to stop delaying the decision.
Whales live in all of the world's oceans, though their specific range varies by species.
Like all mammals, whales breathe air into lungs, are warm-blooded, feed their young milk and have some (although very little) hair. Their bodies resemble the streamlined form of a fish, while the forelimbs or flippers are paddle-shaped. The tail fins, or flukes,brand handbags, enable whales to propel themselves through the water. Most species of whale have a fin on their backs known as a dorsal fin.

收起